Imported Upstream version 2012.01.27upstream-weekly/2012.01.27

21 files changed, 5218 insertions, 0 deletions

diff --git a/src/cmd/go/Makefile b/src/cmd/go/Makefile
new file mode 100644
index 000000000..295a14498
--- /dev/null
+++ b/src/cmd/go/Makefile
@@ -0,0 +1,25 @@
+# Copyright 2009 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../Make.inc
+
+TARG=go
+GOFILES=\
+	build.go\
+	fix.go\
+	get.go\
+	fmt.go\
+	help.go\
+	http.go\
+	list.go\
+	main.go\
+	pkg.go\
+	run.go\
+	test.go\
+	testflag.go\
+	version.go\
+	vet.go\
+	vcs.go\
+
+include ../../Make.cmd
diff --git a/src/cmd/go/bootstrap.go b/src/cmd/go/bootstrap.go
new file mode 100644
index 000000000..bc9a3dbbc
--- /dev/null
+++ b/src/cmd/go/bootstrap.go
@@ -0,0 +1,17 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build cmd_go_bootstrap
+
+// This code is compiled only into the bootstrap 'go' binary.
+// These stubs avoid importing packages with large dependency
+// trees, like the use of "net/http" in vcs.go.
+
+package main
+
+import "errors"
+
+func httpGET(url string) ([]byte, error) {
+	return nil, errors.New("no http in bootstrap go command")
+}
diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
new file mode 100644
index 000000000..cbe36f52e
--- /dev/null
+++ b/src/cmd/go/build.go
@@ -0,0 +1,1142 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"container/heap"
+	"errors"
+	"fmt"
+	"go/build"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+var cmdBuild = &Command{
+	UsageLine: "build [-a] [-n] [-o output] [-p n] [-v] [-x] [importpath... | gofiles...]",
+	Short:     "compile packages and dependencies",
+	Long: `
+Build compiles the packages named by the import paths,
+along with their dependencies, but it does not install the results.
+
+If the arguments are a list of .go files, build treats them as a list
+of source files specifying a single package.
+
+When the command line specifies a single main package,
+build writes the resulting executable to output (default a.out).
+Otherwise build compiles the packages but discards the results,
+serving only as a check that the packages can be built.
+
+The -a flag forces rebuilding of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -v flag prints the names of packages as they are compiled.
+The -x flag prints the commands.
+
+The -o flag specifies the output file name.
+It is an error to use -o when the command line specifies multiple packages.
+
+The -p flag specifies the number of builds that can be run in parallel.
+The default is the number of CPUs available.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go install, go get, go clean.
+	`,
+}
+
+func init() {
+	// break init cycle
+	cmdBuild.Run = runBuild
+	cmdInstall.Run = runInstall
+
+	addBuildFlags(cmdBuild)
+	addBuildFlags(cmdInstall)
+}
+
+// Flags set by multiple commands.
+var buildA bool               // -a flag
+var buildN bool               // -n flag
+var buildP = runtime.NumCPU() // -p flag
+var buildV bool               // -v flag
+var buildX bool               // -x flag
+var buildO = cmdBuild.Flag.String("o", "", "output file")
+
+var buildContext = build.DefaultContext
+
+// addBuildFlags adds the flags common to the build and install commands.
+func addBuildFlags(cmd *Command) {
+	cmd.Flag.BoolVar(&buildA, "a", false, "")
+	cmd.Flag.BoolVar(&buildN, "n", false, "")
+	cmd.Flag.IntVar(&buildP, "p", buildP, "")
+	cmd.Flag.BoolVar(&buildV, "v", false, "")
+	cmd.Flag.BoolVar(&buildX, "x", false, "")
+
+	// TODO(rsc): This -t flag is used by buildscript.sh but
+	// not documented.  Should be documented but the
+	// usage lines are getting too long.  Probably need to say
+	// that these flags are applicable to every command and
+	// document them in one help message instead of on every
+	// command's help message.
+	cmd.Flag.Var((*stringsFlag)(&buildContext.BuildTags), "t", "")
+}
+
+type stringsFlag []string
+
+func (v *stringsFlag) Set(s string) error {
+	*v = append(*v, s)
+	return nil
+}
+
+func (v *stringsFlag) String() string {
+	return "<stringsFlag>"
+}
+
+func runBuild(cmd *Command, args []string) {
+	var b builder
+	b.init()
+
+	var pkgs []*Package
+	if len(args) > 0 && strings.HasSuffix(args[0], ".go") {
+		pkg := goFilesPackage(args, "")
+		pkgs = append(pkgs, pkg)
+	} else {
+		pkgs = packagesForBuild(args)
+	}
+
+	if len(pkgs) == 1 && pkgs[0].Name == "main" && *buildO == "" {
+		*buildO = "a.out"
+	}
+
+	if *buildO != "" {
+		if len(pkgs) > 1 {
+			fatalf("go build: cannot use -o with multiple packages")
+		}
+		p := pkgs[0]
+		p.target = "" // must build - not up to date
+		a := b.action(modeInstall, modeBuild, p)
+		a.target = *buildO
+		b.do(a)
+		return
+	}
+
+	a := &action{}
+	for _, p := range packages(args) {
+		a.deps = append(a.deps, b.action(modeBuild, modeBuild, p))
+	}
+	b.do(a)
+}
+
+var cmdInstall = &Command{
+	UsageLine: "install [-a] [-n] [-p n] [-v] [-x] [importpath...]",
+	Short:     "compile and install packages and dependencies",
+	Long: `
+Install compiles and installs the packages named by the import paths,
+along with their dependencies.
+
+The -a flag forces reinstallation of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -v flag prints the names of packages as they are compiled.
+The -x flag prints the commands.
+
+The -p flag specifies the number of builds that can be run in parallel.
+The default is the number of CPUs available.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go build, go get, go clean.
+	`,
+}
+
+func runInstall(cmd *Command, args []string) {
+	pkgs := packagesForBuild(args)
+
+	var b builder
+	b.init()
+	a := &action{}
+	for _, p := range pkgs {
+		a.deps = append(a.deps, b.action(modeInstall, modeInstall, p))
+	}
+	b.do(a)
+}
+
+// A builder holds global state about a build.
+// It does not hold per-package state, because eventually we will
+// build packages in parallel, and the builder will be shared.
+type builder struct {
+	work        string               // the temporary work directory (ends in filepath.Separator)
+	arch        string               // e.g., "6"
+	goroot      string               // the $GOROOT
+	goarch      string               // the $GOARCH
+	goos        string               // the $GOOS
+	gobin       string               // the $GOBIN
+	exe         string               // the executable suffix - "" or ".exe"
+	gcflags     []string             // additional flags for Go compiler
+	actionCache map[cacheKey]*action // a cache of already-constructed actions
+	mkdirCache  map[string]bool      // a cache of created directories
+
+	output    sync.Mutex
+	scriptDir string // current directory in printed script
+
+	exec      sync.Mutex
+	readySema chan bool
+	ready     actionQueue
+}
+
+// An action represents a single action in the action graph.
+type action struct {
+	p          *Package      // the package this action works on
+	deps       []*action     // actions that must happen before this one
+	triggers   []*action     // inverse of deps
+	cgo        *action       // action for cgo binary if needed
+	args       []string      // additional args for runProgram
+	testOutput *bytes.Buffer // test output buffer
+
+	f          func(*builder, *action) error // the action itself (nil = no-op)
+	ignoreFail bool                          // whether to run f even if dependencies fail
+
+	// Generated files, directories.
+	link   bool   // target is executable, not just package
+	pkgdir string // the -I or -L argument to use when importing this package
+	objdir string // directory for intermediate objects
+	objpkg string // the intermediate package .a file created during the action
+	target string // goal of the action: the created package or executable
+
+	// Execution state.
+	pending  int  // number of deps yet to complete
+	priority int  // relative execution priority
+	failed   bool // whether the action failed
+}
+
+// cacheKey is the key for the action cache.
+type cacheKey struct {
+	mode buildMode
+	p    *Package
+}
+
+// buildMode specifies the build mode:
+// are we just building things or also installing the results?
+type buildMode int
+
+const (
+	modeBuild buildMode = iota
+	modeInstall
+)
+
+func (b *builder) init() {
+	var err error
+	b.actionCache = make(map[cacheKey]*action)
+	b.mkdirCache = make(map[string]bool)
+	b.goarch = buildContext.GOARCH
+	b.goos = buildContext.GOOS
+	b.goroot = build.Path[0].Path
+	b.gobin = build.Path[0].BinDir()
+	if b.goos == "windows" {
+		b.exe = ".exe"
+	}
+	b.gcflags = strings.Fields(os.Getenv("GCFLAGS"))
+
+	b.arch, err = build.ArchChar(b.goarch)
+	if err != nil {
+		fatalf("%s", err)
+	}
+
+	if buildN {
+		b.work = "$WORK"
+	} else {
+		b.work, err = ioutil.TempDir("", "go-build")
+		if err != nil {
+			fatalf("%s", err)
+		}
+		if buildX {
+			fmt.Printf("WORK=%s\n", b.work)
+		}
+		atexit(func() { os.RemoveAll(b.work) })
+	}
+}
+
+// goFilesPackage creates a package for building a collection of Go files
+// (typically named on the command line).  If target is given, the package
+// target is target.  Otherwise, the target is named p.a for
+// package p or named after the first Go file for package main.
+func goFilesPackage(gofiles []string, target string) *Package {
+	// TODO: Remove this restriction.
+	for _, f := range gofiles {
+		if !strings.HasSuffix(f, ".go") || strings.Contains(f, "/") || strings.Contains(f, string(filepath.Separator)) {
+			fatalf("named files must be in current directory and .go files")
+		}
+	}
+
+	// Synthesize fake "directory" that only shows those two files,
+	// to make it look like this is a standard package or
+	// command directory.
+	var dir []os.FileInfo
+	for _, file := range gofiles {
+		fi, err := os.Stat(file)
+		if err != nil {
+			fatalf("%s", err)
+		}
+		if fi.IsDir() {
+			fatalf("%s is a directory, should be a Go file", file)
+		}
+		dir = append(dir, fi)
+	}
+	ctxt := buildContext
+	ctxt.ReadDir = func(string) ([]os.FileInfo, error) { return dir, nil }
+	pwd, _ := os.Getwd()
+	var stk importStack
+	pkg := scanPackage(&ctxt, &build.Tree{Path: "."}, "<command line>", "<command line>", pwd+"/.", &stk)
+	if pkg.Error != nil {
+		fatalf("%s", pkg.Error)
+	}
+	if target != "" {
+		pkg.target = target
+	} else if pkg.Name == "main" {
+		pkg.target = gofiles[0][:len(gofiles[0])-len(".go")]
+	} else {
+		pkg.target = pkg.Name + ".a"
+	}
+	pkg.ImportPath = "_/" + pkg.target
+	return pkg
+}
+
+// action returns the action for applying the given operation (mode) to the package.
+// depMode is the action to use when building dependencies.
+func (b *builder) action(mode buildMode, depMode buildMode, p *Package) *action {
+	key := cacheKey{mode, p}
+	a := b.actionCache[key]
+	if a != nil {
+		return a
+	}
+
+	a = &action{p: p, pkgdir: p.t.PkgDir()}
+	if p.pkgdir != "" { // overrides p.t
+		a.pkgdir = p.pkgdir
+	}
+
+	b.actionCache[key] = a
+
+	for _, p1 := range p.imports {
+		a.deps = append(a.deps, b.action(depMode, depMode, p1))
+	}
+
+	if len(p.CgoFiles) > 0 {
+		var stk importStack
+		p1 := loadPackage("cmd/cgo", &stk)
+		if p1.Error != nil {
+			fatalf("load cmd/cgo: %v", p1.Error)
+		}
+		a.cgo = b.action(depMode, depMode, p1)
+		a.deps = append(a.deps, a.cgo)
+	}
+
+	if p.Standard {
+		switch p.ImportPath {
+		case "builtin", "unsafe":
+			// Fake packages - nothing to build.
+			return a
+		}
+	}
+
+	if !p.Stale && !buildA && p.target != "" {
+		// p.Stale==false implies that p.target is up-to-date.
+		// Record target name for use by actions depending on this one.
+		a.target = p.target
+		return a
+	}
+
+	a.objdir = filepath.Join(b.work, filepath.FromSlash(a.p.ImportPath+"/_obj")) + string(filepath.Separator)
+	a.objpkg = filepath.Join(b.work, filepath.FromSlash(a.p.ImportPath+".a"))
+	a.link = p.Name == "main"
+
+	switch mode {
+	case modeInstall:
+		a.f = (*builder).install
+		a.deps = []*action{b.action(modeBuild, depMode, p)}
+		a.target = a.p.target
+	case modeBuild:
+		a.f = (*builder).build
+		a.target = a.objpkg
+		if a.link {
+			// An executable file.
+			// Have to use something other than .a for the suffix.
+			// It is easier on Windows if we use .exe, so use .exe everywhere.
+			// (This is the name of a temporary file.)
+			a.target = a.objdir + "a.out" + b.exe
+		}
+	}
+
+	return a
+}
+
+// actionList returns the list of actions in the dag rooted at root
+// as visited in a depth-first post-order traversal.
+func actionList(root *action) []*action {
+	seen := map[*action]bool{}
+	all := []*action{}
+	var walk func(*action)
+	walk = func(a *action) {
+		if seen[a] {
+			return
+		}
+		seen[a] = true
+		for _, a1 := range a.deps {
+			walk(a1)
+		}
+		all = append(all, a)
+	}
+	walk(root)
+	return all
+}
+
+// do runs the action graph rooted at root.
+func (b *builder) do(root *action) {
+	// Build list of all actions, assigning depth-first post-order priority.
+	// The original implementation here was a true queue
+	// (using a channel) but it had the effect of getting
+	// distracted by low-level leaf actions to the detriment
+	// of completing higher-level actions.  The order of
+	// work does not matter much to overall execution time,
+	// but when running "go test std" it is nice to see each test
+	// results as soon as possible.  The priorities assigned
+	// ensure that, all else being equal, the execution prefers
+	// to do what it would have done first in a simple depth-first
+	// dependency order traversal.
+	all := actionList(root)
+	for i, a := range all {
+		a.priority = i
+	}
+
+	b.readySema = make(chan bool, len(all))
+	done := make(chan bool)
+
+	// Initialize per-action execution state.
+	for _, a := range all {
+		for _, a1 := range a.deps {
+			a1.triggers = append(a1.triggers, a)
+		}
+		a.pending = len(a.deps)
+		if a.pending == 0 {
+			b.ready.push(a)
+			b.readySema <- true
+		}
+	}
+
+	// Handle runs a single action and takes care of triggering
+	// any actions that are runnable as a result.
+	handle := func(a *action) {
+		var err error
+		if a.f != nil && (!a.failed || a.ignoreFail) {
+			err = a.f(b, a)
+		}
+
+		// The actions run in parallel but all the updates to the
+		// shared work state are serialized through b.exec.
+		b.exec.Lock()
+		defer b.exec.Unlock()
+
+		if err != nil {
+			if err == errPrintedOutput {
+				exitStatus = 2
+			} else {
+				errorf("%s", err)
+			}
+			a.failed = true
+		}
+
+		for _, a0 := range a.triggers {
+			if a.failed {
+				a0.failed = true
+			}
+			if a0.pending--; a0.pending == 0 {
+				b.ready.push(a0)
+				b.readySema <- true
+			}
+		}
+
+		if a == root {
+			close(b.readySema)
+			done <- true
+		}
+	}
+
+	// Kick off goroutines according to parallelism.
+	// If we are using the -n flag (just printing commands)
+	// drop the parallelism to 1, both to make the output
+	// deterministic and because there is no real work anyway.
+	par := buildP
+	if buildN {
+		par = 1
+	}
+	for i := 0; i < par; i++ {
+		go func() {
+			for _ = range b.readySema {
+				// Receiving a value from b.sema entitles
+				// us to take from the ready queue.
+				b.exec.Lock()
+				a := b.ready.pop()
+				b.exec.Unlock()
+				handle(a)
+			}
+		}()
+	}
+
+	<-done
+}
+
+// build is the action for building a single package or command.
+func (b *builder) build(a *action) error {
+	if buildN {
+		// In -n mode, print a banner between packages.
+		// The banner is five lines so that when changes to
+		// different sections of the bootstrap script have to
+		// be merged, the banners give patch something
+		// to use to find its context.
+		fmt.Printf("\n#\n# %s\n#\n\n", a.p.ImportPath)
+	}
+
+	if buildV {
+		fmt.Fprintf(os.Stderr, "%s\n", a.p.ImportPath)
+	}
+
+	// Make build directory.
+	obj := a.objdir
+	if err := b.mkdir(obj); err != nil {
+		return err
+	}
+
+	var gofiles, cfiles, sfiles, objects, cgoObjects []string
+	gofiles = append(gofiles, a.p.GoFiles...)
+	cfiles = append(cfiles, a.p.CFiles...)
+	sfiles = append(sfiles, a.p.SFiles...)
+
+	// Run cgo.
+	if len(a.p.CgoFiles) > 0 {
+		// In a package using cgo, cgo compiles the C and assembly files with gcc.  
+		// There is one exception: runtime/cgo's job is to bridge the
+		// cgo and non-cgo worlds, so it necessarily has files in both.
+		// In that case gcc only gets the gcc_* files.
+		var gccfiles []string
+		if a.p.Standard && a.p.ImportPath == "runtime/cgo" {
+			filter := func(files, nongcc, gcc []string) ([]string, []string) {
+				for _, f := range files {
+					if strings.HasPrefix(f, "gcc_") {
+						gcc = append(gcc, f)
+					} else {
+						nongcc = append(nongcc, f)
+					}
+				}
+				return nongcc, gcc
+			}
+			cfiles, gccfiles = filter(cfiles, cfiles[:0], gccfiles)
+			sfiles, gccfiles = filter(sfiles, sfiles[:0], gccfiles)
+		} else {
+			gccfiles = append(cfiles, sfiles...)
+			cfiles = nil
+			sfiles = nil
+		}
+
+		outGo, outObj, err := b.cgo(a.p, a.cgo.target, obj, gccfiles)
+		if err != nil {
+			return err
+		}
+		cgoObjects = append(cgoObjects, outObj...)
+		gofiles = append(gofiles, outGo...)
+	}
+
+	// Prepare Go import path list.
+	inc := b.includeArgs("-I", a.deps)
+
+	// Compile Go.
+	if len(gofiles) > 0 {
+		out := "_go_." + b.arch
+		gcargs := []string{"-p", a.p.ImportPath}
+		if a.p.Standard && a.p.ImportPath == "runtime" {
+			// runtime compiles with a special 6g flag to emit
+			// additional reflect type data.
+			gcargs = append(gcargs, "-+")
+		}
+		if err := b.gc(a.p, obj+out, gcargs, inc, gofiles); err != nil {
+			return err
+		}
+		objects = append(objects, out)
+	}
+
+	// Copy .h files named for goos or goarch or goos_goarch
+	// to names using GOOS and GOARCH.
+	// For example, defs_linux_amd64.h becomes defs_GOOS_GOARCH.h.
+	_goos_goarch := "_" + b.goos + "_" + b.goarch + ".h"
+	_goos := "_" + b.goos + ".h"
+	_goarch := "_" + b.goarch + ".h"
+	for _, file := range a.p.HFiles {
+		switch {
+		case strings.HasSuffix(file, _goos_goarch):
+			targ := file[:len(file)-len(_goos_goarch)] + "_GOOS_GOARCH.h"
+			if err := b.copyFile(obj+targ, filepath.Join(a.p.Dir, file), 0666); err != nil {
+				return err
+			}
+		case strings.HasSuffix(file, _goarch):
+			targ := file[:len(file)-len(_goarch)] + "_GOARCH.h"
+			if err := b.copyFile(obj+targ, filepath.Join(a.p.Dir, file), 0666); err != nil {
+				return err
+			}
+		case strings.HasSuffix(file, _goos):
+			targ := file[:len(file)-len(_goos)] + "_GOOS.h"
+			if err := b.copyFile(obj+targ, filepath.Join(a.p.Dir, file), 0666); err != nil {
+				return err
+			}
+		}
+	}
+
+	for _, file := range cfiles {
+		out := file[:len(file)-len(".c")] + "." + b.arch
+		if err := b.cc(a.p, obj, obj+out, file); err != nil {
+			return err
+		}
+		objects = append(objects, out)
+	}
+
+	// Assemble .s files.
+	for _, file := range sfiles {
+		out := file[:len(file)-len(".s")] + "." + b.arch
+		if err := b.asm(a.p, obj, obj+out, file); err != nil {
+			return err
+		}
+		objects = append(objects, out)
+	}
+
+	// NOTE(rsc): On Windows, it is critically important that the
+	// gcc-compiled objects (cgoObjects) be listed after the ordinary
+	// objects in the archive.  I do not know why this is.
+	// http://golang.org/issue/2601
+	objects = append(objects, cgoObjects...)
+
+	// Pack into archive in obj directory
+	if err := b.gopack(a.p, obj, a.objpkg, objects); err != nil {
+		return err
+	}
+
+	// Link if needed.
+	if a.link {
+		// The compiler only cares about direct imports, but the
+		// linker needs the whole dependency tree.
+		all := actionList(a)
+		all = all[:len(all)-1] // drop a
+		inc := b.includeArgs("-L", all)
+		if err := b.ld(a.p, a.target, inc, a.objpkg); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// install is the action for installing a single package or executable.
+func (b *builder) install(a *action) error {
+	a1 := a.deps[0]
+	perm := os.FileMode(0666)
+	if a1.link {
+		perm = 0777
+	}
+
+	// make target directory
+	dir, _ := filepath.Split(a.target)
+	if dir != "" {
+		if err := b.mkdir(dir); err != nil {
+			return err
+		}
+	}
+
+	return b.copyFile(a.target, a1.target, perm)
+}
+
+// includeArgs returns the -I or -L directory list for access
+// to the results of the list of actions.
+func (b *builder) includeArgs(flag string, all []*action) []string {
+	inc := []string{}
+	incMap := map[string]bool{
+		b.work:                 true, // handled later
+		build.Path[0].PkgDir(): true, // goroot
+		"":                     true, // ignore empty strings
+	}
+
+	// Look in the temporary space for results of test-specific actions.
+	// This is the $WORK/my/package/_test directory for the
+	// package being built, so there are few of these.
+	for _, a1 := range all {
+		if dir := a1.pkgdir; dir != a1.p.t.PkgDir() && !incMap[dir] {
+			incMap[dir] = true
+			inc = append(inc, flag, dir)
+		}
+	}
+
+	// Also look in $WORK for any non-test packages that have
+	// been built but not installed.
+	inc = append(inc, flag, b.work)
+
+	// Finally, look in the installed package directories for each action.
+	for _, a1 := range all {
+		if dir := a1.pkgdir; dir == a1.p.t.PkgDir() && !incMap[dir] {
+			incMap[dir] = true
+			inc = append(inc, flag, dir)
+		}
+	}
+
+	return inc
+}
+
+// removeByRenaming removes file name by moving it to a tmp
+// directory and deleting the target if possible.
+func removeByRenaming(name string) error {
+	f, err := ioutil.TempFile("", "")
+	if err != nil {
+		return err
+	}
+	tmpname := f.Name()
+	f.Close()
+	err = os.Remove(tmpname)
+	if err != nil {
+		return err
+	}
+	err = os.Rename(name, tmpname)
+	if err != nil {
+		// assume name file does not exists,
+		// otherwise later code will fail.
+		return nil
+	}
+	err = os.Remove(tmpname)
+	if err != nil {
+		// TODO(brainman): file is locked and can't be deleted.
+		// We need to come up with a better way of doing it. 
+	}
+	return nil
+}
+
+// copyFile is like 'cp src dst'.
+func (b *builder) copyFile(dst, src string, perm os.FileMode) error {
+	if buildN || buildX {
+		b.showcmd("", "cp %s %s", src, dst)
+		if buildN {
+			return nil
+		}
+	}
+
+	sf, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer sf.Close()
+	os.Remove(dst)
+	df, err := os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
+	if err != nil {
+		if runtime.GOOS != "windows" {
+			return err
+		}
+		// Windows does not allow to replace binary file
+		// while it is executing. We will cheat.
+		err = removeByRenaming(dst)
+		if err != nil {
+			return err
+		}
+		df, err = os.OpenFile(dst, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
+		if err != nil {
+			return err
+		}
+	}
+	_, err = io.Copy(df, sf)
+	df.Close()
+	if err != nil {
+		os.Remove(dst)
+		return err
+	}
+	return nil
+}
+
+// fmtcmd formats a command in the manner of fmt.Sprintf but also:
+//
+//	If dir is non-empty and the script is not in dir right now,
+//	fmtcmd inserts "cd dir\n" before the command.
+//
+//	fmtcmd replaces the value of b.work with $WORK.
+//	fmtcmd replaces the value of b.goroot with $GOROOT.
+//	fmtcmd replaces the value of b.gobin with $GOBIN.
+//
+//	fmtcmd replaces the name of the current directory with dot (.)
+//	but only when it is at the beginning of a space-separated token.
+//
+func (b *builder) fmtcmd(dir string, format string, args ...interface{}) string {
+	cmd := fmt.Sprintf(format, args...)
+	if dir != "" {
+		cmd = strings.Replace(" "+cmd, " "+dir, " .", -1)[1:]
+		if b.scriptDir != dir {
+			b.scriptDir = dir
+			cmd = "cd " + dir + "\n" + cmd
+		}
+	}
+	cmd = strings.Replace(cmd, b.work, "$WORK", -1)
+	cmd = strings.Replace(cmd, b.gobin, "$GOBIN", -1)
+	cmd = strings.Replace(cmd, b.goroot, "$GOROOT", -1)
+	return cmd
+}
+
+// showcmd prints the given command to standard output
+// for the implementation of -n or -x.
+func (b *builder) showcmd(dir string, format string, args ...interface{}) {
+	b.output.Lock()
+	defer b.output.Unlock()
+	fmt.Println(b.fmtcmd(dir, format, args...))
+}
+
+// showOutput prints "# desc" followed by the given output.
+// The output is expected to contain references to 'dir', usually
+// the source directory for the package that has failed to build.
+// showOutput rewrites mentions of dir with a relative path to dir
+// when the relative path is shorter.  This is usually more pleasant.
+// For example, if fmt doesn't compile and we are in src/pkg/html,
+// the output is
+//
+//	$ go build
+//	# fmt
+//	../fmt/print.go:1090: undefined: asdf
+//	$
+//
+// instead of
+//
+//	$ go build
+//	# fmt
+//	/usr/gopher/go/src/pkg/fmt/print.go:1090: undefined: asdf
+//	$
+//
+// showOutput also replaces references to the work directory with $WORK.
+//
+func (b *builder) showOutput(dir, desc, out string) {
+	prefix := "# " + desc
+	suffix := "\n" + out
+	pwd, _ := os.Getwd()
+	if reldir, err := filepath.Rel(pwd, dir); err == nil && len(reldir) < len(dir) {
+		suffix = strings.Replace(suffix, " "+dir, " "+reldir, -1)
+		suffix = strings.Replace(suffix, "\n"+dir, "\n"+reldir, -1)
+	}
+	suffix = strings.Replace(suffix, " "+b.work, " $WORK", -1)
+
+	b.output.Lock()
+	defer b.output.Unlock()
+	fmt.Print(prefix, suffix)
+}
+
+// relPaths returns a copy of paths with absolute paths
+// made relative to the current directory if they would be shorter.
+func relPaths(paths []string) []string {
+	var out []string
+	pwd, _ := os.Getwd()
+	for _, p := range paths {
+		rel, err := filepath.Rel(pwd, p)
+		if err == nil && len(rel) < len(p) {
+			p = rel
+		}
+		out = append(out, p)
+	}
+	return out
+}
+
+// errPrintedOutput is a special error indicating that a command failed
+// but that it generated output as well, and that output has already
+// been printed, so there's no point showing 'exit status 1' or whatever
+// the wait status was.  The main executor, builder.do, knows not to
+// print this error.
+var errPrintedOutput = errors.New("already printed output - no need to show error")
+
+// run runs the command given by cmdline in the directory dir.
+// If the commnd fails, run prints information about the failure
+// and returns a non-nil error.
+func (b *builder) run(dir string, desc string, cmdargs ...interface{}) error {
+	out, err := b.runOut(dir, desc, cmdargs...)
+	if len(out) > 0 {
+		if out[len(out)-1] != '\n' {
+			out = append(out, '\n')
+		}
+		if desc == "" {
+			desc = b.fmtcmd(dir, "%s", strings.Join(stringList(cmdargs...), " "))
+		}
+		b.showOutput(dir, desc, string(out))
+		if err != nil {
+			err = errPrintedOutput
+		}
+	}
+	return err
+}
+
+// runOut runs the command given by cmdline in the directory dir.
+// It returns the command output and any errors that occurred.
+func (b *builder) runOut(dir string, desc string, cmdargs ...interface{}) ([]byte, error) {
+	cmdline := stringList(cmdargs...)
+	if buildN || buildX {
+		b.showcmd(dir, "%s", strings.Join(cmdline, " "))
+		if buildN {
+			return nil, nil
+		}
+	}
+
+	var buf bytes.Buffer
+	cmd := exec.Command(cmdline[0], cmdline[1:]...)
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+	cmd.Dir = dir
+	// TODO: cmd.Env
+	err := cmd.Run()
+	return buf.Bytes(), err
+}
+
+// mkdir makes the named directory.
+func (b *builder) mkdir(dir string) error {
+	b.exec.Lock()
+	defer b.exec.Unlock()
+	// We can be a little aggressive about being
+	// sure directories exist.  Skip repeated calls.
+	if b.mkdirCache[dir] {
+		return nil
+	}
+	b.mkdirCache[dir] = true
+
+	if buildN || buildX {
+		b.showcmd("", "mkdir -p %s", dir)
+		if buildN {
+			return nil
+		}
+	}
+
+	if err := os.MkdirAll(dir, 0777); err != nil {
+		return err
+	}
+	return nil
+}
+
+// mkAbs returns an absolute path corresponding to
+// evaluating f in the directory dir.
+// We always pass absolute paths of source files so that
+// the error messages will include the full path to a file
+// in need of attention.
+func mkAbs(dir, f string) string {
+	// Leave absolute paths alone.
+	// Also, during -n mode we use the pseudo-directory $WORK
+	// instead of creating an actual work directory that won't be used.
+	// Leave paths beginning with $WORK alone too.
+	if filepath.IsAbs(f) || strings.HasPrefix(f, "$WORK") {
+		return f
+	}
+	return filepath.Join(dir, f)
+}
+
+// gc runs the Go compiler in a specific directory on a set of files
+// to generate the named output file. 
+func (b *builder) gc(p *Package, ofile string, gcargs, importArgs []string, gofiles []string) error {
+	args := stringList(b.arch+"g", "-o", ofile, b.gcflags, gcargs, importArgs)
+	for _, f := range gofiles {
+		args = append(args, mkAbs(p.Dir, f))
+	}
+	return b.run(p.Dir, p.ImportPath, args)
+}
+
+// asm runs the assembler in a specific directory on a specific file
+// to generate the named output file. 
+func (b *builder) asm(p *Package, obj, ofile, sfile string) error {
+	sfile = mkAbs(p.Dir, sfile)
+	return b.run(p.Dir, p.ImportPath, b.arch+"a", "-I", obj, "-o", ofile, "-DGOOS_"+b.goos, "-DGOARCH_"+b.goarch, sfile)
+}
+
+// gopack runs the assembler in a specific directory to create
+// an archive from a set of object files.
+// typically it is run in the object directory.
+func (b *builder) gopack(p *Package, objDir, afile string, ofiles []string) error {
+	var absOfiles []string
+	for _, f := range ofiles {
+		absOfiles = append(absOfiles, mkAbs(objDir, f))
+	}
+	return b.run(p.Dir, p.ImportPath, "gopack", "grc", mkAbs(objDir, afile), absOfiles)
+}
+
+// ld runs the linker to create a package starting at mainpkg.
+func (b *builder) ld(p *Package, out string, importArgs []string, mainpkg string) error {
+	return b.run(p.Dir, p.ImportPath, b.arch+"l", "-o", out, importArgs, mainpkg)
+}
+
+// cc runs the gc-toolchain C compiler in a directory on a C file
+// to produce an output file.
+func (b *builder) cc(p *Package, objdir, ofile, cfile string) error {
+	inc := filepath.Join(b.goroot, "pkg", fmt.Sprintf("%s_%s", b.goos, b.goarch))
+	cfile = mkAbs(p.Dir, cfile)
+	return b.run(p.Dir, p.ImportPath, b.arch+"c", "-FVw",
+		"-I", objdir, "-I", inc, "-o", ofile,
+		"-DGOOS_"+b.goos, "-DGOARCH_"+b.goarch, cfile)
+}
+
+// gcc runs the gcc C compiler to create an object from a single C file.
+func (b *builder) gcc(p *Package, out string, flags []string, cfile string) error {
+	cfile = mkAbs(p.Dir, cfile)
+	return b.run(p.Dir, p.ImportPath, b.gccCmd(p.Dir), flags, "-o", out, "-c", cfile)
+}
+
+// gccld runs the gcc linker to create an executable from a set of object files
+func (b *builder) gccld(p *Package, out string, flags []string, obj []string) error {
+	return b.run(p.Dir, p.ImportPath, b.gccCmd(p.Dir), "-o", out, obj, flags)
+}
+
+// gccCmd returns a gcc command line prefix
+func (b *builder) gccCmd(objdir string) []string {
+	// TODO: HOST_CC?
+	a := []string{"gcc", "-I", objdir, "-g", "-O2"}
+
+	// Definitely want -fPIC but on Windows gcc complains
+	// "-fPIC ignored for target (all code is position independent)"
+	if b.goos != "windows" {
+		a = append(a, "-fPIC")
+	}
+	switch b.arch {
+	case "8":
+		a = append(a, "-m32")
+	case "6":
+		a = append(a, "-m64")
+	}
+	// gcc-4.5 and beyond require explicit "-pthread" flag
+	// for multithreading with pthread library.
+	if buildContext.CgoEnabled {
+		switch b.goos {
+		case "windows":
+			a = append(a, "-mthreads")
+		default:
+			a = append(a, "-pthread")
+		}
+	}
+	return a
+}
+
+var cgoRe = regexp.MustCompile(`[/\\:]`)
+
+func (b *builder) cgo(p *Package, cgoExe, obj string, gccfiles []string) (outGo, outObj []string, err error) {
+	if b.goos != runtime.GOOS {
+		return nil, nil, errors.New("cannot use cgo when compiling for a different operating system")
+	}
+
+	outObj = append(outObj, "") // for importObj, at end of function
+
+	cgoCFLAGS := stringList(p.info.CgoCFLAGS)
+	cgoLDFLAGS := stringList(p.info.CgoLDFLAGS)
+	if pkgs := p.info.CgoPkgConfig; len(pkgs) > 0 {
+		out, err := b.runOut(p.Dir, p.ImportPath, "pkg-config", "--cflags", pkgs)
+		if err != nil {
+			return nil, nil, err
+		}
+		if len(out) > 0 {
+			cgoCFLAGS = append(cgoCFLAGS, strings.Fields(string(out))...)
+		}
+		out, err = b.runOut(p.Dir, p.ImportPath, "pkg-config", "--libs", pkgs)
+		if err != nil {
+			return nil, nil, err
+		}
+		if len(out) > 0 {
+			cgoLDFLAGS = append(cgoLDFLAGS, strings.Fields(string(out))...)
+		}
+	}
+
+	// cgo
+	// TODO: CGOPKGPATH, CGO_FLAGS?
+	gofiles := []string{obj + "_cgo_gotypes.go"}
+	cfiles := []string{"_cgo_main.c", "_cgo_export.c"}
+	for _, fn := range p.CgoFiles {
+		f := cgoRe.ReplaceAllString(fn[:len(fn)-2], "_")
+		gofiles = append(gofiles, obj+f+"cgo1.go")
+		cfiles = append(cfiles, f+"cgo2.c")
+	}
+	defunC := obj + "_cgo_defun.c"
+	// TODO: make cgo not depend on $GOARCH?
+	var runtimeFlag []string
+	if p.Standard && p.ImportPath == "runtime/cgo" {
+		runtimeFlag = []string{"-import_runtime_cgo=false"}
+	}
+	if err := b.run(p.Dir, p.ImportPath, cgoExe, "-objdir", obj, runtimeFlag, "--", p.CgoFiles); err != nil {
+		return nil, nil, err
+	}
+	outGo = append(outGo, gofiles...)
+
+	// cc _cgo_defun.c
+	defunObj := obj + "_cgo_defun." + b.arch
+	if err := b.cc(p, obj, defunObj, defunC); err != nil {
+		return nil, nil, err
+	}
+	outObj = append(outObj, defunObj)
+
+	// gcc
+	var linkobj []string
+	for _, cfile := range cfiles {
+		ofile := obj + cfile[:len(cfile)-1] + "o"
+		if err := b.gcc(p, ofile, cgoCFLAGS, obj+cfile); err != nil {
+			return nil, nil, err
+		}
+		linkobj = append(linkobj, ofile)
+		if !strings.HasSuffix(ofile, "_cgo_main.o") {
+			outObj = append(outObj, ofile)
+		}
+	}
+	for _, file := range gccfiles {
+		ofile := obj + cgoRe.ReplaceAllString(file[:len(file)-1], "_") + "o"
+		if err := b.gcc(p, ofile, cgoCFLAGS, file); err != nil {
+			return nil, nil, err
+		}
+		linkobj = append(linkobj, ofile)
+		outObj = append(outObj, ofile)
+	}
+	dynobj := obj + "_cgo_.o"
+	if err := b.gccld(p, dynobj, cgoLDFLAGS, linkobj); err != nil {
+		return nil, nil, err
+	}
+
+	// cgo -dynimport
+	importC := obj + "_cgo_import.c"
+	if err := b.run(p.Dir, p.ImportPath, cgoExe, "-objdir", obj, "-dynimport", dynobj, "-dynout", importC); err != nil {
+		return nil, nil, err
+	}
+
+	// cc _cgo_import.ARCH
+	importObj := obj + "_cgo_import." + b.arch
+	if err := b.cc(p, obj, importObj, importC); err != nil {
+		return nil, nil, err
+	}
+
+	// NOTE(rsc): The importObj is a 5c/6c/8c object and on Windows
+	// must be processed before the gcc-generated objects.
+	// Put it first.  We left room above.  http://golang.org/issue/2601
+	outObj[0] = importObj
+
+	return outGo, outObj, nil
+}
+
+// An actionQueue is a priority queue of actions.
+type actionQueue []*action
+
+// Implement heap.Interface
+func (q *actionQueue) Len() int           { return len(*q) }
+func (q *actionQueue) Swap(i, j int)      { (*q)[i], (*q)[j] = (*q)[j], (*q)[i] }
+func (q *actionQueue) Less(i, j int) bool { return (*q)[i].priority < (*q)[j].priority }
+func (q *actionQueue) Push(x interface{}) { *q = append(*q, x.(*action)) }
+func (q *actionQueue) Pop() interface{} {
+	n := len(*q) - 1
+	x := (*q)[n]
+	*q = (*q)[:n]
+	return x
+}
+
+func (q *actionQueue) push(a *action) {
+	heap.Push(q, a)
+}
+
+func (q *actionQueue) pop() *action {
+	return heap.Pop(q).(*action)
+}
diff --git a/src/cmd/go/doc.go b/src/cmd/go/doc.go
new file mode 100644
index 000000000..27be32bf3
--- /dev/null
+++ b/src/cmd/go/doc.go
@@ -0,0 +1,601 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Go is a tool for managing Go source code.
+
+Usage: go command [arguments]
+
+The commands are:
+
+    build       compile packages and dependencies
+    doc         run godoc on package sources
+    fix         run gofix on packages
+    fmt         run gofmt on package sources
+    get         download and install packages and dependencies
+    install     compile and install packages and dependencies
+    list        list packages
+    run         compile and run Go program
+    test        test packages
+    version     print Go version
+    vet         run govet on packages
+
+Use "go help [command]" for more information about a command.
+
+Additional help topics:
+
+    gopath      GOPATH environment variable
+    importpath  description of import paths
+    remote      remote import path syntax
+    testflag    description of testing flags
+    testfunc    description of testing functions
+
+Use "go help [topic]" for more information about that topic.
+
+
+Compile packages and dependencies
+
+Usage:
+
+	go build [-a] [-n] [-o output] [-p n] [-v] [-x] [importpath... | gofiles...]
+
+Build compiles the packages named by the import paths,
+along with their dependencies, but it does not install the results.
+
+If the arguments are a list of .go files, build treats them as a list
+of source files specifying a single package.
+
+When the command line specifies a single main package,
+build writes the resulting executable to output (default a.out).
+Otherwise build compiles the packages but discards the results,
+serving only as a check that the packages can be built.
+
+The -a flag forces rebuilding of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -v flag prints the names of packages as they are compiled.
+The -x flag prints the commands.
+
+The -o flag specifies the output file name.
+It is an error to use -o when the command line specifies multiple packages.
+
+The -p flag specifies the number of builds that can be run in parallel.
+The default is the number of CPUs available.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go install, go get, go clean.
+
+
+Run godoc on package sources
+
+Usage:
+
+	go doc [importpath...]
+
+Doc runs the godoc command on the packages named by the
+import paths.
+
+For more about godoc, see 'godoc godoc'.
+For more about import paths, see 'go help importpath'.
+
+To run godoc with specific options, run godoc itself.
+
+See also: go fix, go fmt, go vet.
+
+
+Run gofix on packages
+
+Usage:
+
+	go fix [importpath...]
+
+Fix runs the gofix command on the packages named by the import paths.
+
+For more about gofix, see 'godoc gofix'.
+For more about import paths, see 'go help importpath'.
+
+To run gofix with specific options, run gofix itself.
+
+See also: go fmt, go vet.
+
+
+Run gofmt on package sources
+
+Usage:
+
+	go fmt [importpath...]
+
+Fmt runs the command 'gofmt -l -w' on the packages named
+by the import paths.  It prints the names of the files that are modified.
+
+For more about gofmt, see 'godoc gofmt'.
+For more about import paths, see 'go help importpath'.
+
+To run gofmt with specific options, run gofmt itself.
+
+See also: go doc, go fix, go vet.
+
+
+Download and install packages and dependencies
+
+Usage:
+
+	go get [-a] [-d] [-fix] [-n] [-p n] [-u] [-v] [-x] [importpath...]
+
+Get downloads and installs the packages named by the import paths,
+along with their dependencies.
+
+The -a, -n, -v, -x, and -p flags have the same meaning as in 'go build'
+and 'go install'.  See 'go help install'.
+
+The -d flag instructs get to stop after downloading the packages; that is,
+it instructs get not to install the packages.
+
+The -fix flag instructs get to run gofix on the downloaded packages
+before resolving dependencies or building the code.
+
+The -u flag instructs get to use the network to update the named packages
+and their dependencies.  By default, get uses the network to check out 
+missing packages but does not use it to look for updates to existing packages.
+
+TODO: Explain versions better.
+
+For more about import paths, see 'go help importpath'.
+
+For more about how 'go get' finds source code to
+download, see 'go help remote'.
+
+See also: go build, go install, go clean.
+
+
+Compile and install packages and dependencies
+
+Usage:
+
+	go install [-a] [-n] [-p n] [-v] [-x] [importpath...]
+
+Install compiles and installs the packages named by the import paths,
+along with their dependencies.
+
+The -a flag forces reinstallation of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -v flag prints the names of packages as they are compiled.
+The -x flag prints the commands.
+
+The -p flag specifies the number of builds that can be run in parallel.
+The default is the number of CPUs available.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go build, go get, go clean.
+
+
+List packages
+
+Usage:
+
+	go list [-e] [-f format] [-json] [importpath...]
+
+List lists the packages named by the import paths, one per line.
+
+The default output shows the package import path:
+
+    code.google.com/p/google-api-go-client/books/v1
+    code.google.com/p/goauth2/oauth
+    code.google.com/p/sqlite
+
+The -f flag specifies an alternate format for the list,
+using the syntax of package template.  The default output
+is equivalent to -f '{{.ImportPath}}'.  The struct
+being passed to the template is:
+
+    type Package struct {
+        Name       string // package name
+        Doc        string // package documentation string
+        ImportPath string // import path of package in dir
+        Dir        string // directory containing package sources
+        Version    string // version of installed package (TODO)
+        Stale      bool   // would 'go install' do anything for this package?
+
+        // Source files
+        GoFiles      []string // .go source files (excluding CgoFiles, TestGoFiles, and XTestGoFiles)
+        TestGoFiles  []string // _test.go source files internal to the package they are testing
+        XTestGoFiles []string // _test.go source files external to the package they are testing
+        CFiles       []string // .c source files
+        HFiles       []string // .h source files
+        SFiles       []string // .s source files
+        CgoFiles     []string // .go sources files that import "C"
+
+        // Dependency information
+        Imports []string // import paths used by this package
+        Deps    []string // all (recursively) imported dependencies
+
+        // Error information
+        Incomplete bool            // this package or a dependency has an error
+        Error *PackageError        // error loading package
+        DepsErrors []*PackageError // errors loading dependencies
+    }
+
+The -json flag causes the package data to be printed in JSON format
+instead of using the template format.
+
+The -e flag changes the handling of erroneous packages, those that
+cannot be found or are malformed.  By default, the list command
+prints an error to standard error for each erroneous package and
+omits the packages from consideration during the usual printing.
+With the -e flag, the list command never prints errors to standard
+error and instead processes the erroneous packages with the usual
+printing.  Erroneous packages will have a non-empty ImportPath and
+a non-nil Error field; other information may or may not be missing
+(zeroed).
+
+For more about import paths, see 'go help importpath'.
+
+
+Compile and run Go program
+
+Usage:
+
+	go run [-a] [-n] [-x] gofiles... [arguments...]
+
+Run compiles and runs the main package comprising the named Go source files.
+
+The -a flag forces reinstallation of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -x flag prints the commands.
+
+See also: go build.
+
+
+Test packages
+
+Usage:
+
+	go test [-c] [-file a.go -file b.go ...] [-p n] [-x] [importpath...] [flags for test binary]
+
+'Go test' automates testing the packages named by the import paths.
+It prints a summary of the test results in the format:
+
+	ok   archive/tar   0.011s
+	FAIL archive/zip   0.022s
+	ok   compress/gzip 0.033s
+	...
+
+followed by detailed output for each failed package.
+
+'Go test' recompiles each package along with any files with names matching
+the file pattern "*_test.go".  These additional files can contain test functions,
+benchmark functions, and example functions.  See 'go help testfunc' for more.
+
+By default, go test needs no arguments.  It compiles and tests the package
+with source in the current directory, including tests, and runs the tests.
+If file names are given (with flag -file=test.go, one per extra test source file),
+only those test files are added to the package.  (The non-test files are always
+compiled.)
+
+The package is built in a temporary directory so it does not interfere with the
+non-test installation.
+
+See 'go help testflag' for details about flags handled by 'go test'
+and the test binary.
+
+See 'go help importpath' for more about import paths.
+
+See also: go build, go vet.
+
+
+Print Go version
+
+Usage:
+
+	go version
+
+Version prints the Go version, as reported by runtime.Version.
+
+
+Run govet on packages
+
+Usage:
+
+	go vet [importpath...]
+
+Vet runs the govet command on the packages named by the import paths.
+
+For more about govet, see 'godoc govet'.
+For more about import paths, see 'go help importpath'.
+
+To run govet with specific options, run govet itself.
+
+See also: go fmt, go fix.
+
+
+GOPATH environment variable
+
+The GOPATH environment variable lists places to look for Go code.
+On Unix, the value is a colon-separated string.
+On Windows, the value is a semicolon-separated string.
+On Plan 9, the value is a list.
+
+GOPATH must be set to build and install packages outside the
+standard Go tree.
+
+Each directory listed in GOPATH must have a prescribed structure:
+
+The src/ directory holds source code.  The path below 'src'
+determines the import path or executable name.
+
+The pkg/ directory holds installed package objects.
+As in the Go tree, each target operating system and
+architecture pair has its own subdirectory of pkg
+(pkg/GOOS_GOARCH).
+
+If DIR is a directory listed in the GOPATH, a package with
+source in DIR/src/foo/bar can be imported as "foo/bar" and
+has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a".
+
+The bin/ directory holds compiled commands.
+Each command is named for its source directory, but only
+the final element, not the entire path.  That is, the
+command with source in DIR/src/foo/quux is installed into
+DIR/bin/quux, not DIR/bin/foo/quux.  The foo/ is stripped
+so that you can add DIR/bin to your PATH to get at the
+installed commands.
+
+Here's an example directory layout:
+
+    GOPATH=/home/user/gocode
+
+    /home/user/gocode/
+        src/
+            foo/
+                bar/               (go code in package bar)
+                    x.go
+                quux/              (go code in package main)
+                    y.go
+        bin/
+            quux                   (installed command)
+        pkg/
+            linux_amd64/
+                foo/
+                    bar.a          (installed package object)
+
+Go searches each directory listed in GOPATH to find source code,
+but new packages are always downloaded into the first directory 
+in the list.
+
+
+Description of import paths
+
+Many commands apply to a set of packages named by import paths:
+
+	go action [importpath...]
+
+An import path that is a rooted path or that begins with
+a . or .. element is interpreted as a file system path and
+denotes the package in that directory.
+
+Otherwise, the import path P denotes the package found in
+the directory DIR/src/P for some DIR listed in the GOPATH
+environment variable (see 'go help gopath'). 
+
+If no import paths are given, the action applies to the
+package in the current directory.
+
+The special import path "all" expands to all package directories
+found in all the GOPATH trees.  For example, 'go list all' 
+lists all the packages on the local system.
+
+The special import path "std" is like all but expands to just the
+packages in the standard Go library.
+
+An import path is a pattern if it includes one or more "..." wildcards,
+each of which can match any string, including the empty string and
+strings containing slashes.  Such a pattern expands to all package
+directories found in the GOPATH trees with names matching the
+patterns.  For example, encoding/... expands to all packages
+in the encoding tree.
+
+An import path can also name a package to be downloaded from
+a remote repository.  Run 'go help remote' for details.
+
+Every package in a program must have a unique import path.
+By convention, this is arranged by starting each path with a
+unique prefix that belongs to you.  For example, paths used
+internally at Google all begin with 'google', and paths
+denoting remote repositories begin with the path to the code,
+such as 'code.google.com/p/project'.
+
+
+Remote import path syntax
+
+An import path (see 'go help importpath') denotes a package
+stored in the local file system.  Certain import paths also
+describe how to obtain the source code for the package using
+a revision control system.
+
+A few common code hosting sites have special syntax:
+
+	BitBucket (Mercurial)
+
+		import "bitbucket.org/user/project"
+		import "bitbucket.org/user/project/sub/directory"
+
+	GitHub (Git)
+
+		import "github.com/user/project"
+		import "github.com/user/project/sub/directory"
+
+	Google Code Project Hosting (Git, Mercurial, Subversion)
+
+		import "code.google.com/p/project"
+		import "code.google.com/p/project/sub/directory"
+
+		import "code.google.com/p/project.subrepository"
+		import "code.google.com/p/project.subrepository/sub/directory"
+
+	Launchpad (Bazaar)
+
+		import "launchpad.net/project"
+		import "launchpad.net/project/series"
+		import "launchpad.net/project/series/sub/directory"
+
+		import "launchpad.net/~user/project/branch"
+		import "launchpad.net/~user/project/branch/sub/directory"
+
+For code hosted on other servers, an import path of the form
+
+	repository.vcs/path
+
+specifies the given repository, with or without the .vcs suffix,
+using the named version control system, and then the path inside
+that repository.  The supported version control systems are:
+
+	Bazaar      .bzr
+	Git         .git
+	Mercurial   .hg
+	Subversion  .svn
+
+For example,
+
+	import "example.org/user/foo.hg"
+
+denotes the root directory of the Mercurial repository at
+example.org/user/foo or foo.hg, and
+
+	import "example.org/repo.git/foo/bar"
+
+denotes the foo/bar directory of the Git repository at
+example.com/repo or repo.git.
+
+When a version control system supports multiple protocols,
+each is tried in turn when downloading.  For example, a Git
+download tries git://, then https://, then http://.
+
+New downloaded packages are written to the first directory
+listed in the GOPATH environment variable (see 'go help gopath').
+
+The go command attempts to download the version of the
+package appropriate for the Go release being used.
+Run 'go help install' for more.
+
+
+Description of testing flags
+
+The 'go test' command takes both flags that apply to 'go test' itself
+and flags that apply to the resulting test binary.
+
+The flags handled by 'go test' are:
+
+	-c  Compile the test binary to test.out but do not run it.
+
+	-file a.go
+	    Use only the tests in the source file a.go.
+	    Multiple -file flags may be provided.
+
+	-p n
+	    Compile and test up to n packages in parallel.
+	    The default value is the number of CPUs available.
+
+	-x  Print each subcommand go test executes.
+
+The resulting test binary, called test.out, has its own flags:
+
+	-test.v
+	    Verbose output: log all tests as they are run.
+
+	-test.run pattern
+	    Run only those tests matching the regular expression.
+
+	-test.bench pattern
+	    Run benchmarks matching the regular expression.
+	    By default, no benchmarks run.
+
+	-test.cpuprofile cpu.out
+	    Write a CPU profile to the specified file before exiting.
+
+	-test.memprofile mem.out
+	    Write a memory profile to the specified file when all tests
+	    are complete.
+
+	-test.memprofilerate n
+	    Enable more precise (and expensive) memory profiles by setting
+	    runtime.MemProfileRate.  See 'godoc runtime MemProfileRate'.
+	    To profile all memory allocations, use -test.memprofilerate=1
+	    and set the environment variable GOGC=off to disable the
+	    garbage collector, provided the test can run in the available
+	    memory without garbage collection.
+
+	-test.parallel n
+	    Allow parallel execution of test functions that call t.Parallel.
+	    The value of this flag is the maximum number of tests to run
+	    simultaneously; by default, it is set to the value of GOMAXPROCS.
+
+	-test.short
+	    Tell long-running tests to shorten their run time.
+	    It is off by default but set during all.bash so that installing
+	    the Go tree can run a sanity check but not spend time running
+	    exhaustive tests.
+
+	-test.timeout t
+		If a test runs longer than t, panic.
+
+	-test.benchtime n
+		Run enough iterations of each benchmark to take n seconds.
+		The default is 1 second.
+
+	-test.cpu 1,2,4
+	    Specify a list of GOMAXPROCS values for which the tests or 
+	    benchmarks should be executed.  The default is the current value
+	    of GOMAXPROCS.
+
+For convenience, each of these -test.X flags of the test binary is
+also available as the flag -X in 'go test' itself.  Flags not listed
+here are passed through unaltered.  For instance, the command
+
+	go test -x -v -cpuprofile=prof.out -dir=testdata -update -file x_test.go
+
+will compile the test binary using x_test.go and then run it as
+
+	test.out -test.v -test.cpuprofile=prof.out -dir=testdata -update
+
+
+Description of testing functions
+
+The 'go test' command expects to find test, benchmark, and example functions
+in the "*_test.go" files corresponding to the package under test.
+
+A test function is one named TestXXX (where XXX is any alphanumeric string
+not starting with a lower case letter) and should have the signature,
+
+	func TestXXX(t *testing.T) { ... }
+
+A benchmark function is one named BenchmarkXXX and should have the signature,
+
+	func BenchmarkXXX(b *testing.B) { ... }
+
+An example function is similar to a test function but, instead of using *testing.T
+to report success or failure, prints output to os.Stdout and os.Stderr.
+That output is compared against the function's doc comment.
+An example without a doc comment is compiled but not executed.
+
+Godoc displays the body of ExampleXXX to demonstrate the use
+of the function, constant, or variable XXX.  An example of a method M with
+receiver type T or *T is named ExampleT_M.  There may be multiple examples
+for a given function, constant, or variable, distinguished by a trailing _xxx,
+where xxx is a suffix not beginning with an upper case letter.
+
+Here is an example of an example:
+
+	// The output of this example function.
+	func ExamplePrintln() {
+		Println("The output of this example function.")
+	}
+
+See the documentation of the testing package for more information.
+
+
+*/
+package documentation
+
+// NOTE: cmdDoc is in fmt.go.
diff --git a/src/cmd/go/fix.go b/src/cmd/go/fix.go
new file mode 100644
index 000000000..bae9f5c98
--- /dev/null
+++ b/src/cmd/go/fix.go
@@ -0,0 +1,30 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var cmdFix = &Command{
+	Run:       runFix,
+	UsageLine: "fix [importpath...]",
+	Short:     "run gofix on packages",
+	Long: `
+Fix runs the gofix command on the packages named by the import paths.
+
+For more about gofix, see 'godoc gofix'.
+For more about import paths, see 'go help importpath'.
+
+To run gofix with specific options, run gofix itself.
+
+See also: go fmt, go vet.
+	`,
+}
+
+func runFix(cmd *Command, args []string) {
+	for _, pkg := range packages(args) {
+		// Use pkg.gofiles instead of pkg.Dir so that
+		// the command only applies to this package,
+		// not to packages in subdirectories.
+		run(stringList("gofix", relPaths(pkg.gofiles)))
+	}
+}
diff --git a/src/cmd/go/fmt.go b/src/cmd/go/fmt.go
new file mode 100644
index 000000000..4a47e2ea2
--- /dev/null
+++ b/src/cmd/go/fmt.go
@@ -0,0 +1,54 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var cmdFmt = &Command{
+	Run:       runFmt,
+	UsageLine: "fmt [importpath...]",
+	Short:     "run gofmt on package sources",
+	Long: `
+Fmt runs the command 'gofmt -l -w' on the packages named
+by the import paths.  It prints the names of the files that are modified.
+
+For more about gofmt, see 'godoc gofmt'.
+For more about import paths, see 'go help importpath'.
+
+To run gofmt with specific options, run gofmt itself.
+
+See also: go doc, go fix, go vet.
+	`,
+}
+
+func runFmt(cmd *Command, args []string) {
+	for _, pkg := range packages(args) {
+		// Use pkg.gofiles instead of pkg.Dir so that
+		// the command only applies to this package,
+		// not to packages in subdirectories.
+		run(stringList("gofmt", "-l", "-w", relPaths(pkg.gofiles)))
+	}
+}
+
+var cmdDoc = &Command{
+	Run:       runDoc,
+	UsageLine: "doc [importpath...]",
+	Short:     "run godoc on package sources",
+	Long: `
+Doc runs the godoc command on the packages named by the
+import paths.
+
+For more about godoc, see 'godoc godoc'.
+For more about import paths, see 'go help importpath'.
+
+To run godoc with specific options, run godoc itself.
+
+See also: go fix, go fmt, go vet.
+	`,
+}
+
+func runDoc(cmd *Command, args []string) {
+	for _, pkg := range packages(args) {
+		run("godoc", pkg.Dir)
+	}
+}
diff --git a/src/cmd/go/get.go b/src/cmd/go/get.go
new file mode 100644
index 000000000..cd57d3025
--- /dev/null
+++ b/src/cmd/go/get.go
@@ -0,0 +1,269 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// TODO: Dashboard upload
+
+package main
+
+import (
+	"fmt"
+	"go/build"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+var cmdGet = &Command{
+	UsageLine: "get [-a] [-d] [-fix] [-n] [-p n] [-u] [-v] [-x] [importpath...]",
+	Short:     "download and install packages and dependencies",
+	Long: `
+Get downloads and installs the packages named by the import paths,
+along with their dependencies.
+
+The -a, -n, -v, -x, and -p flags have the same meaning as in 'go build'
+and 'go install'.  See 'go help install'.
+
+The -d flag instructs get to stop after downloading the packages; that is,
+it instructs get not to install the packages.
+
+The -fix flag instructs get to run gofix on the downloaded packages
+before resolving dependencies or building the code.
+
+The -u flag instructs get to use the network to update the named packages
+and their dependencies.  By default, get uses the network to check out 
+missing packages but does not use it to look for updates to existing packages.
+
+TODO: Explain versions better.
+
+For more about import paths, see 'go help importpath'.
+
+For more about how 'go get' finds source code to
+download, see 'go help remote'.
+
+See also: go build, go install, go clean.
+	`,
+}
+
+var getD = cmdGet.Flag.Bool("d", false, "")
+var getU = cmdGet.Flag.Bool("u", false, "")
+var getFix = cmdGet.Flag.Bool("fix", false, "")
+
+func init() {
+	addBuildFlags(cmdGet)
+	cmdGet.Run = runGet // break init loop
+}
+
+func runGet(cmd *Command, args []string) {
+	// Phase 1.  Download/update.
+	args = importPaths(args)
+	var stk importStack
+	for _, arg := range args {
+		download(arg, &stk)
+	}
+	exitIfErrors()
+
+	if *getD {
+		// download only
+		return
+	}
+
+	// Phase 2. Install.
+
+	// Code we downloaded and all code that depends on it
+	// needs to be evicted from the package cache so that
+	// the information will be recomputed.  Instead of keeping
+	// track of the reverse dependency information, evict
+	// everything.
+	for name := range packageCache {
+		delete(packageCache, name)
+	}
+
+	runInstall(cmd, args)
+}
+
+// downloadCache records the import paths we have already
+// considered during the download, to avoid duplicate work when
+// there is more than one dependency sequence leading to
+// a particular package.
+var downloadCache = map[string]bool{}
+
+// downloadRootCache records the version control repository
+// root directories we have already considered during the download.
+// For example, all the packages in the code.google.com/p/codesearch repo
+// share the same root (the directory for that path), and we only need
+// to run the hg commands to consider each repository once.
+var downloadRootCache = map[string]bool{}
+
+// download runs the download half of the get command
+// for the package named by the argument.
+func download(arg string, stk *importStack) {
+	p := loadPackage(arg, stk)
+
+	// There's nothing to do if this is a package in the standard library.
+	if p.Standard {
+		return
+	}
+
+	// Only process each package once.
+	if downloadCache[arg] {
+		return
+	}
+	downloadCache[arg] = true
+
+	// Download if the package is missing, or update if we're using -u.
+	if p.Dir == "" || *getU {
+		// The actual download.
+		stk.push(p.ImportPath)
+		defer stk.pop()
+		if err := downloadPackage(p); err != nil {
+			errorf("%s", &PackageError{stk.copy(), err.Error()})
+			return
+		}
+
+		// Reread the package information from the updated files.
+		p = reloadPackage(arg, stk)
+		if p.Error != nil {
+			errorf("%s", p.Error)
+			return
+		}
+	}
+
+	if *getFix {
+		run(stringList("gofix", relPaths(p.gofiles)))
+
+		// The imports might have changed, so reload again.
+		p = reloadPackage(arg, stk)
+		if p.Error != nil {
+			errorf("%s", p.Error)
+			return
+		}
+	}
+
+	// Process dependencies, now that we know what they are.
+	for _, dep := range p.deps {
+		download(dep.ImportPath, stk)
+	}
+}
+
+// downloadPackage runs the create or download command
+// to make the first copy of or update a copy of the given package.
+func downloadPackage(p *Package) error {
+	// Analyze the import path to determine the version control system,
+	// repository, and the import path for the root of the repository.
+	vcs, repo, rootPath, err := vcsForImportPath(p.ImportPath)
+	if err != nil {
+		return err
+	}
+	if p.t == nil {
+		// Package not found.  Put in first directory of $GOPATH or else $GOROOT.
+		p.t = build.Path[0] // $GOROOT
+		if len(build.Path) > 1 {
+			p.t = build.Path[1] // first in $GOPATH
+		}
+		p.Dir = filepath.Join(p.t.SrcDir(), p.ImportPath)
+	}
+	root := filepath.Join(p.t.SrcDir(), rootPath)
+
+	// If we've considered this repository already, don't do it again.
+	if downloadRootCache[root] {
+		return nil
+	}
+	downloadRootCache[root] = true
+
+	if buildV {
+		fmt.Fprintf(os.Stderr, "%s (download)\n", rootPath)
+	}
+
+	// Check that this is an appropriate place for the repo to be checked out.
+	// The target directory must either not exist or have a repo checked out already.
+	meta := filepath.Join(root, "."+vcs.cmd)
+	st, err := os.Stat(meta)
+	if err == nil && !st.IsDir() {
+		return fmt.Errorf("%s exists but is not a directory", meta)
+	}
+	if err != nil {
+		// Metadata directory does not exist.  Prepare to checkout new copy.
+		// Some version control tools require the target directory not to exist.
+		// We require that too, just to avoid stepping on existing work.
+		if _, err := os.Stat(root); err == nil {
+			return fmt.Errorf("%s exists but %s does not - stale checkout?", root, meta)
+		}
+		// Some version control tools require the parent of the target to exist.
+		parent, _ := filepath.Split(root)
+		if err := os.MkdirAll(parent, 0777); err != nil {
+			return err
+		}
+		if err = vcs.create(root, repo); err != nil {
+			return err
+		}
+	} else {
+		// Metadata directory does exist; download incremental updates.
+		if err = vcs.download(root); err != nil {
+			return err
+		}
+	}
+
+	// Select and sync to appropriate version of the repository.
+	tags, err := vcs.tags(root)
+	if err != nil {
+		return err
+	}
+	vers := runtime.Version()
+	if i := strings.Index(vers, " "); i >= 0 {
+		vers = vers[:i]
+	}
+	tag := selectTag(vers, tags)
+	if tag == "" {
+		tag = vcs.tagDefault
+	}
+	if err := vcs.tagSync(root, tag); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// selectTag returns the closest matching tag for a given version.
+// Closest means the latest one that is not after the current release.
+// Version "release.rN" matches tags of the form "go.rN" (N being a decimal).
+// Version "weekly.YYYY-MM-DD" matches tags like "go.weekly.YYYY-MM-DD".
+func selectTag(goVersion string, tags []string) (match string) {
+	const rPrefix = "release.r"
+	if strings.HasPrefix(goVersion, rPrefix) {
+		p := "go.r"
+		v, err := strconv.ParseFloat(goVersion[len(rPrefix):], 64)
+		if err != nil {
+			return ""
+		}
+		var matchf float64
+		for _, t := range tags {
+			if !strings.HasPrefix(t, p) {
+				continue
+			}
+			tf, err := strconv.ParseFloat(t[len(p):], 64)
+			if err != nil {
+				continue
+			}
+			if matchf < tf && tf <= v {
+				match, matchf = t, tf
+			}
+		}
+	}
+	const wPrefix = "weekly."
+	if strings.HasPrefix(goVersion, wPrefix) {
+		p := "go.weekly."
+		v := goVersion[len(wPrefix):]
+		for _, t := range tags {
+			if !strings.HasPrefix(t, p) {
+				continue
+			}
+			if match < t && t[len(p):] <= v {
+				match = t
+			}
+		}
+	}
+	return match
+}
diff --git a/src/cmd/go/help.go b/src/cmd/go/help.go
new file mode 100644
index 000000000..33716eff9
--- /dev/null
+++ b/src/cmd/go/help.go
@@ -0,0 +1,185 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var helpImportpath = &Command{
+	UsageLine: "importpath",
+	Short:     "description of import paths",
+	Long: `
+Many commands apply to a set of packages named by import paths:
+
+	go action [importpath...]
+
+An import path that is a rooted path or that begins with
+a . or .. element is interpreted as a file system path and
+denotes the package in that directory.
+
+Otherwise, the import path P denotes the package found in
+the directory DIR/src/P for some DIR listed in the GOPATH
+environment variable (see 'go help gopath'). 
+
+If no import paths are given, the action applies to the
+package in the current directory.
+
+The special import path "all" expands to all package directories
+found in all the GOPATH trees.  For example, 'go list all' 
+lists all the packages on the local system.
+
+The special import path "std" is like all but expands to just the
+packages in the standard Go library.
+
+An import path is a pattern if it includes one or more "..." wildcards,
+each of which can match any string, including the empty string and
+strings containing slashes.  Such a pattern expands to all package
+directories found in the GOPATH trees with names matching the
+patterns.  For example, encoding/... expands to all packages
+in the encoding tree.
+
+An import path can also name a package to be downloaded from
+a remote repository.  Run 'go help remote' for details.
+
+Every package in a program must have a unique import path.
+By convention, this is arranged by starting each path with a
+unique prefix that belongs to you.  For example, paths used
+internally at Google all begin with 'google', and paths
+denoting remote repositories begin with the path to the code,
+such as 'code.google.com/p/project'.
+	`,
+}
+
+var helpRemote = &Command{
+	UsageLine: "remote",
+	Short:     "remote import path syntax",
+	Long: `
+
+An import path (see 'go help importpath') denotes a package
+stored in the local file system.  Certain import paths also
+describe how to obtain the source code for the package using
+a revision control system.
+
+A few common code hosting sites have special syntax:
+
+	BitBucket (Mercurial)
+
+		import "bitbucket.org/user/project"
+		import "bitbucket.org/user/project/sub/directory"
+
+	GitHub (Git)
+
+		import "github.com/user/project"
+		import "github.com/user/project/sub/directory"
+
+	Google Code Project Hosting (Git, Mercurial, Subversion)
+
+		import "code.google.com/p/project"
+		import "code.google.com/p/project/sub/directory"
+
+		import "code.google.com/p/project.subrepository"
+		import "code.google.com/p/project.subrepository/sub/directory"
+
+	Launchpad (Bazaar)
+
+		import "launchpad.net/project"
+		import "launchpad.net/project/series"
+		import "launchpad.net/project/series/sub/directory"
+
+		import "launchpad.net/~user/project/branch"
+		import "launchpad.net/~user/project/branch/sub/directory"
+
+For code hosted on other servers, an import path of the form
+
+	repository.vcs/path
+
+specifies the given repository, with or without the .vcs suffix,
+using the named version control system, and then the path inside
+that repository.  The supported version control systems are:
+
+	Bazaar      .bzr
+	Git         .git
+	Mercurial   .hg
+	Subversion  .svn
+
+For example,
+
+	import "example.org/user/foo.hg"
+
+denotes the root directory of the Mercurial repository at
+example.org/user/foo or foo.hg, and
+
+	import "example.org/repo.git/foo/bar"
+
+denotes the foo/bar directory of the Git repository at
+example.com/repo or repo.git.
+
+When a version control system supports multiple protocols,
+each is tried in turn when downloading.  For example, a Git
+download tries git://, then https://, then http://.
+
+New downloaded packages are written to the first directory
+listed in the GOPATH environment variable (see 'go help gopath').
+
+The go command attempts to download the version of the
+package appropriate for the Go release being used.
+Run 'go help install' for more.
+	`,
+}
+
+var helpGopath = &Command{
+	UsageLine: "gopath",
+	Short:     "GOPATH environment variable",
+	Long: `
+The GOPATH environment variable lists places to look for Go code.
+On Unix, the value is a colon-separated string.
+On Windows, the value is a semicolon-separated string.
+On Plan 9, the value is a list.
+
+GOPATH must be set to build and install packages outside the
+standard Go tree.
+
+Each directory listed in GOPATH must have a prescribed structure:
+
+The src/ directory holds source code.  The path below 'src'
+determines the import path or executable name.
+
+The pkg/ directory holds installed package objects.
+As in the Go tree, each target operating system and
+architecture pair has its own subdirectory of pkg
+(pkg/GOOS_GOARCH).
+
+If DIR is a directory listed in the GOPATH, a package with
+source in DIR/src/foo/bar can be imported as "foo/bar" and
+has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a".
+
+The bin/ directory holds compiled commands.
+Each command is named for its source directory, but only
+the final element, not the entire path.  That is, the
+command with source in DIR/src/foo/quux is installed into
+DIR/bin/quux, not DIR/bin/foo/quux.  The foo/ is stripped
+so that you can add DIR/bin to your PATH to get at the
+installed commands.
+
+Here's an example directory layout:
+
+    GOPATH=/home/user/gocode
+
+    /home/user/gocode/
+        src/
+            foo/
+                bar/               (go code in package bar)
+                    x.go
+                quux/              (go code in package main)
+                    y.go
+        bin/
+            quux                   (installed command)
+        pkg/
+            linux_amd64/
+                foo/
+                    bar.a          (installed package object)
+
+Go searches each directory listed in GOPATH to find source code,
+but new packages are always downloaded into the first directory 
+in the list.
+	`,
+}
diff --git a/src/cmd/go/http.go b/src/cmd/go/http.go
new file mode 100644
index 000000000..8d9b2a165
--- /dev/null
+++ b/src/cmd/go/http.go
@@ -0,0 +1,35 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !cmd_go_bootstrap
+
+// This code is compiled into the real 'go' binary, but it is not
+// compiled into the binary that is built during all.bash, so as
+// to avoid needing to build net (and thus use cgo) during the
+// bootstrap process.
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+// httpGET returns the data from an HTTP GET request for the given URL.
+func httpGET(url string) ([]byte, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		return nil, fmt.Errorf("%s: %s", url, resp.Status)
+	}
+	b, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %v", url, err)
+	}
+	return b, nil
+}
diff --git a/src/cmd/go/list.go b/src/cmd/go/list.go
new file mode 100644
index 000000000..af211f98d
--- /dev/null
+++ b/src/cmd/go/list.go
@@ -0,0 +1,114 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"text/template"
+)
+
+var cmdList = &Command{
+	UsageLine: "list [-e] [-f format] [-json] [importpath...]",
+	Short:     "list packages",
+	Long: `
+List lists the packages named by the import paths, one per line.
+
+The default output shows the package import path:
+
+    code.google.com/p/google-api-go-client/books/v1
+    code.google.com/p/goauth2/oauth
+    code.google.com/p/sqlite
+
+The -f flag specifies an alternate format for the list,
+using the syntax of package template.  The default output
+is equivalent to -f '{{.ImportPath}}'.  The struct
+being passed to the template is:
+
+    type Package struct {
+        Name       string // package name
+        Doc        string // package documentation string
+        ImportPath string // import path of package in dir
+        Dir        string // directory containing package sources
+        Version    string // version of installed package (TODO)
+        Stale      bool   // would 'go install' do anything for this package?
+
+        // Source files
+        GoFiles      []string // .go source files (excluding CgoFiles, TestGoFiles, and XTestGoFiles)
+        TestGoFiles  []string // _test.go source files internal to the package they are testing
+        XTestGoFiles []string // _test.go source files external to the package they are testing
+        CFiles       []string // .c source files
+        HFiles       []string // .h source files
+        SFiles       []string // .s source files
+        CgoFiles     []string // .go sources files that import "C"
+
+        // Dependency information
+        Imports []string // import paths used by this package
+        Deps    []string // all (recursively) imported dependencies
+        
+        // Error information
+        Incomplete bool            // this package or a dependency has an error
+        Error *PackageError        // error loading package
+        DepsErrors []*PackageError // errors loading dependencies
+    }
+
+The -json flag causes the package data to be printed in JSON format
+instead of using the template format.
+
+The -e flag changes the handling of erroneous packages, those that
+cannot be found or are malformed.  By default, the list command
+prints an error to standard error for each erroneous package and
+omits the packages from consideration during the usual printing.
+With the -e flag, the list command never prints errors to standard
+error and instead processes the erroneous packages with the usual
+printing.  Erroneous packages will have a non-empty ImportPath and
+a non-nil Error field; other information may or may not be missing
+(zeroed).
+
+For more about import paths, see 'go help importpath'.
+	`,
+}
+
+func init() {
+	cmdList.Run = runList // break init cycle
+}
+
+var listE = cmdList.Flag.Bool("e", false, "")
+var listFmt = cmdList.Flag.String("f", "{{.ImportPath}}", "")
+var listJson = cmdList.Flag.Bool("json", false, "")
+var nl = []byte{'\n'}
+
+func runList(cmd *Command, args []string) {
+	var do func(*Package)
+	if *listJson {
+		do = func(p *Package) {
+			b, err := json.MarshalIndent(p, "", "\t")
+			if err != nil {
+				fatalf("%s", err)
+			}
+			os.Stdout.Write(b)
+			os.Stdout.Write(nl)
+		}
+	} else {
+		tmpl, err := template.New("main").Parse(*listFmt + "\n")
+		if err != nil {
+			fatalf("%s", err)
+		}
+		do = func(p *Package) {
+			if err := tmpl.Execute(os.Stdout, p); err != nil {
+				fatalf("%s", err)
+			}
+		}
+	}
+
+	load := packages
+	if *listE {
+		load = packagesAndErrors
+	}
+
+	for _, pkg := range load(args) {
+		do(pkg)
+	}
+}
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
new file mode 100644
index 000000000..ca3b1188a
--- /dev/null
+++ b/src/cmd/go/main.go
@@ -0,0 +1,485 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/build"
+	"io"
+	"log"
+	"os"
+	"os/exec"
+	"path"
+	"path/filepath"
+	"regexp"
+	"strings"
+	"text/template"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A Command is an implementation of a go command
+// like go build or go fix.
+type Command struct {
+	// Run runs the command.
+	// The args are the arguments after the command name.
+	Run func(cmd *Command, args []string)
+
+	// UsageLine is the one-line usage message.
+	// The first word in the line is taken to be the command name.
+	UsageLine string
+
+	// Short is the short description shown in the 'go help' output.
+	Short string
+
+	// Long is the long message shown in the 'go help <this-command>' output.
+	Long string
+
+	// Flag is a set of flags specific to this command.
+	Flag flag.FlagSet
+
+	// CustomFlags indicates that the command will do its own
+	// flag parsing.
+	CustomFlags bool
+}
+
+// Name returns the command's name: the first word in the usage line.
+func (c *Command) Name() string {
+	name := c.UsageLine
+	i := strings.Index(name, " ")
+	if i >= 0 {
+		name = name[:i]
+	}
+	return name
+}
+
+func (c *Command) Usage() {
+	fmt.Fprintf(os.Stderr, "usage: %s\n\n", c.UsageLine)
+	fmt.Fprintf(os.Stderr, "%s\n", strings.TrimSpace(c.Long))
+	os.Exit(2)
+}
+
+// Commands lists the available commands and help topics.
+// The order here is the order in which they are printed by 'go help'.
+var commands = []*Command{
+	cmdBuild,
+	cmdDoc,
+	cmdFix,
+	cmdFmt,
+	cmdGet,
+	cmdInstall,
+	cmdList,
+	cmdRun,
+	cmdTest,
+	cmdVersion,
+	cmdVet,
+
+	helpGopath,
+	helpImportpath,
+	helpRemote,
+	helpTestflag,
+	helpTestfunc,
+}
+
+var exitStatus = 0
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	log.SetFlags(0)
+
+	args := flag.Args()
+	if len(args) < 1 {
+		usage()
+	}
+
+	if args[0] == "help" {
+		help(args[1:])
+		return
+	}
+
+	for _, cmd := range commands {
+		if cmd.Name() == args[0] && cmd.Run != nil {
+			cmd.Flag.Usage = func() { cmd.Usage() }
+			if cmd.CustomFlags {
+				args = args[1:]
+			} else {
+				cmd.Flag.Parse(args[1:])
+				args = cmd.Flag.Args()
+			}
+			cmd.Run(cmd, args)
+			exit()
+			return
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "Unknown command %#q\n\n", args[0])
+	usage()
+}
+
+var usageTemplate = `Go is a tool for managing Go source code.
+
+Usage: go command [arguments]
+
+The commands are:
+{{range .}}{{if .Run}}
+    {{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
+
+Use "go help [command]" for more information about a command.
+
+Additional help topics:
+{{range .}}{{if not .Run}}
+    {{.Name | printf "%-11s"}} {{.Short}}{{end}}{{end}}
+
+Use "go help [topic]" for more information about that topic.
+
+`
+
+var helpTemplate = `{{if .Run}}usage: go {{.UsageLine}}
+
+{{end}}{{.Long | trim}}
+`
+
+var documentationTemplate = `// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+{{range .}}{{if .Short}}{{.Short | capitalize}}
+
+{{end}}{{if .Run}}Usage:
+
+	go {{.UsageLine}}
+
+{{end}}{{.Long | trim}}
+
+
+{{end}}*/
+package documentation
+
+// NOTE: cmdDoc is in fmt.go.
+`
+
+// tmpl executes the given template text on data, writing the result to w.
+func tmpl(w io.Writer, text string, data interface{}) {
+	t := template.New("top")
+	t.Funcs(template.FuncMap{"trim": strings.TrimSpace, "capitalize": capitalize})
+	template.Must(t.Parse(text))
+	if err := t.Execute(w, data); err != nil {
+		panic(err)
+	}
+}
+
+func capitalize(s string) string {
+	if s == "" {
+		return s
+	}
+	r, n := utf8.DecodeRuneInString(s)
+	return string(unicode.ToTitle(r)) + s[n:]
+}
+
+func printUsage(w io.Writer) {
+	tmpl(w, usageTemplate, commands)
+}
+
+func usage() {
+	printUsage(os.Stderr)
+	os.Exit(2)
+}
+
+// help implements the 'help' command.
+func help(args []string) {
+	if len(args) == 0 {
+		printUsage(os.Stdout)
+		// not exit 2: succeeded at 'go help'.
+		return
+	}
+	if len(args) != 1 {
+		fmt.Fprintf(os.Stderr, "usage: go help command\n\nToo many arguments given.\n")
+		os.Exit(2) // failed at 'go help'
+	}
+
+	arg := args[0]
+
+	// 'go help documentation' generates doc.go.
+	if arg == "documentation" {
+		buf := new(bytes.Buffer)
+		printUsage(buf)
+		usage := &Command{Long: buf.String()}
+		tmpl(os.Stdout, documentationTemplate, append([]*Command{usage}, commands...))
+		return
+	}
+
+	for _, cmd := range commands {
+		if cmd.Name() == arg {
+			tmpl(os.Stdout, helpTemplate, cmd)
+			// not exit 2: succeeded at 'go help cmd'.
+			return
+		}
+	}
+
+	fmt.Fprintf(os.Stderr, "Unknown help topic %#q.  Run 'go help'.\n", arg)
+	os.Exit(2) // failed at 'go help cmd'
+}
+
+// importPaths returns the import paths to use for the given command line.
+func importPaths(args []string) []string {
+	if len(args) == 0 {
+		return []string{"."}
+	}
+	var out []string
+	for _, a := range args {
+		if isLocalPath(a) && strings.Contains(a, "...") {
+			out = append(out, allPackagesInFS(a)...)
+			continue
+		}
+		if a == "all" || a == "std" || strings.Contains(a, "...") {
+			out = append(out, allPackages(a)...)
+			continue
+		}
+		out = append(out, a)
+	}
+	return out
+}
+
+var atexitFuncs []func()
+
+func atexit(f func()) {
+	atexitFuncs = append(atexitFuncs, f)
+}
+
+func exit() {
+	for _, f := range atexitFuncs {
+		f()
+	}
+	os.Exit(exitStatus)
+}
+
+func fatalf(format string, args ...interface{}) {
+	errorf(format, args...)
+	exit()
+}
+
+func errorf(format string, args ...interface{}) {
+	log.Printf(format, args...)
+	exitStatus = 1
+}
+
+var logf = log.Printf
+
+func exitIfErrors() {
+	if exitStatus != 0 {
+		exit()
+	}
+}
+
+func run(cmdargs ...interface{}) {
+	cmdline := stringList(cmdargs...)
+	cmd := exec.Command(cmdline[0], cmdline[1:]...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	if err := cmd.Run(); err != nil {
+		errorf("%v", err)
+	}
+}
+
+func runOut(dir string, cmdargs ...interface{}) []byte {
+	cmdline := stringList(cmdargs...)
+	cmd := exec.Command(cmdline[0], cmdline[1:]...)
+	cmd.Dir = dir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		os.Stderr.Write(out)
+		errorf("%v", err)
+		out = nil
+	}
+	return out
+}
+
+// matchPattern(pattern)(name) reports whether
+// name matches pattern.  Pattern is a limited glob
+// pattern in which '...' means 'any string' and there
+// is no other special syntax.
+func matchPattern(pattern string) func(name string) bool {
+	re := regexp.QuoteMeta(pattern)
+	re = strings.Replace(re, `\.\.\.`, `.*`, -1)
+	reg := regexp.MustCompile(`^` + re + `$`)
+	return func(name string) bool {
+		return reg.MatchString(name)
+	}
+}
+
+// allPackages returns all the packages that can be found
+// under the $GOPATH directories and $GOROOT matching pattern.
+// The pattern is either "all" (all packages), "std" (standard packages)
+// or a path including "...".
+func allPackages(pattern string) []string {
+	match := func(string) bool { return true }
+	if pattern != "all" && pattern != "std" {
+		match = matchPattern(pattern)
+	}
+
+	have := map[string]bool{
+		"builtin": true, // ignore pseudo-package that exists only for documentation
+	}
+	if !buildContext.CgoEnabled {
+		have["runtime/cgo"] = true // ignore during walk
+	}
+	var pkgs []string
+
+	// Commands
+	goroot := build.Path[0].Path
+	cmd := filepath.Join(goroot, "src/cmd") + string(filepath.Separator)
+	filepath.Walk(cmd, func(path string, fi os.FileInfo, err error) error {
+		if err != nil || !fi.IsDir() {
+			return nil
+		}
+		name := path[len(cmd):]
+		// Commands are all in cmd/, not in subdirectories.
+		if strings.Contains(name, string(filepath.Separator)) {
+			return filepath.SkipDir
+		}
+
+		_, err = build.ScanDir(path)
+		if err != nil {
+			return nil
+		}
+
+		// We use, e.g., cmd/gofmt as the pseudo import path for gofmt.
+		name = "cmd/" + name
+		if !have[name] {
+			have[name] = true
+			if match(name) {
+				pkgs = append(pkgs, name)
+			}
+		}
+		return nil
+	})
+
+	for _, t := range build.Path {
+		if pattern == "std" && !t.Goroot {
+			continue
+		}
+		src := t.SrcDir() + string(filepath.Separator)
+		filepath.Walk(src, func(path string, fi os.FileInfo, err error) error {
+			if err != nil || !fi.IsDir() {
+				return nil
+			}
+
+			// Avoid .foo, _foo, and testdata directory trees.
+			_, elem := filepath.Split(path)
+			if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
+				return filepath.SkipDir
+			}
+
+			name := filepath.ToSlash(path[len(src):])
+			if pattern == "std" && strings.Contains(name, ".") {
+				return filepath.SkipDir
+			}
+			if have[name] {
+				return nil
+			}
+			have[name] = true
+
+			_, err = build.ScanDir(path)
+			if err != nil {
+				return nil
+			}
+
+			if match(name) {
+				pkgs = append(pkgs, name)
+			}
+
+			// Avoid go/build test data.
+			// TODO: Move it into a testdata directory.
+			if path == filepath.Join(build.Path[0].SrcDir(), "go/build") {
+				return filepath.SkipDir
+			}
+
+			return nil
+		})
+	}
+
+	if len(pkgs) == 0 {
+		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
+	}
+	return pkgs
+}
+
+// allPackagesInFS is like allPackages but is passed a pattern
+// beginning ./ or ../, meaning it should scan the tree rooted
+// at the given directory.  There are ... in the pattern too.
+func allPackagesInFS(pattern string) []string {
+	// Find directory to begin the scan.
+	// Could be smarter but this one optimization
+	// is enough for now, since ... is usually at the
+	// end of a path.
+	i := strings.Index(pattern, "...")
+	dir, _ := path.Split(pattern[:i])
+
+	// pattern begins with ./ or ../.
+	// path.Clean will discard the ./ but not the ../.
+	// We need to preserve the ./ for pattern matching
+	// and in the returned import paths.
+	prefix := ""
+	if strings.HasPrefix(pattern, "./") {
+		prefix = "./"
+	}
+	match := matchPattern(pattern)
+
+	var pkgs []string
+	filepath.Walk(dir, func(path string, fi os.FileInfo, err error) error {
+		if err != nil || !fi.IsDir() {
+			return nil
+		}
+
+		// Avoid .foo, _foo, and testdata directory trees.
+		_, elem := filepath.Split(path)
+		if strings.HasPrefix(elem, ".") || strings.HasPrefix(elem, "_") || elem == "testdata" {
+			return filepath.SkipDir
+		}
+
+		name := prefix + filepath.ToSlash(path)
+		if !match(name) {
+			return nil
+		}
+		if _, err = build.ScanDir(path); err != nil {
+			return nil
+		}
+		pkgs = append(pkgs, name)
+		return nil
+	})
+
+	if len(pkgs) == 0 {
+		fmt.Fprintf(os.Stderr, "warning: %q matched no packages\n", pattern)
+	}
+	return pkgs
+}
+
+// stringList's arguments should be a sequence of string or []string values.
+// stringList flattens them into a single []string.
+func stringList(args ...interface{}) []string {
+	var x []string
+	for _, arg := range args {
+		switch arg := arg.(type) {
+		case []string:
+			x = append(x, arg...)
+		case string:
+			x = append(x, arg)
+		default:
+			panic("stringList: invalid argument")
+		}
+	}
+	return x
+}
+
+// isLocalPath returns true if arg is an import path denoting
+// a local file system directory.  That is, it returns true if the
+// path begins with ./ or ../ .
+func isLocalPath(arg string) bool {
+	return arg == "." || arg == ".." || strings.HasPrefix(arg, "./") || strings.HasPrefix(arg, "../")
+}
diff --git a/src/cmd/go/mkdoc.sh b/src/cmd/go/mkdoc.sh
new file mode 100755
index 000000000..7768baeb6
--- /dev/null
+++ b/src/cmd/go/mkdoc.sh
@@ -0,0 +1,8 @@
+#!/bin/sh
+# Copyright 2012 The Go Authors.  All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+go help documentation > doc.go
+gofmt -w doc.go
+
diff --git a/src/cmd/go/pkg.go b/src/cmd/go/pkg.go
new file mode 100644
index 000000000..09fa67127
--- /dev/null
+++ b/src/cmd/go/pkg.go
@@ -0,0 +1,445 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"go/build"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"time"
+)
+
+// A Package describes a single package found in a directory.
+type Package struct {
+	// Note: These fields are part of the go command's public API.
+	// See list.go.  It is okay to add fields, but not to change or
+	// remove existing ones.  Keep in sync with list.go
+	ImportPath string        // import path of package in dir
+	Name       string        `json:",omitempty"` // package name
+	Doc        string        `json:",omitempty"` // package documentation string
+	Dir        string        `json:",omitempty"` // directory containing package sources
+	Version    string        `json:",omitempty"` // version of installed package (TODO)
+	Standard   bool          `json:",omitempty"` // is this package part of the standard Go library?
+	Stale      bool          `json:",omitempty"` // would 'go install' do anything for this package?
+	Incomplete bool          `json:",omitempty"` // was there an error loading this package or dependencies?
+	Error      *PackageError `json:",omitempty"` // error loading this package (not dependencies)
+
+	// Source files
+	GoFiles      []string `json:",omitempty"` // .go source files (excluding CgoFiles, TestGoFiles and XTestGoFiles)
+	TestGoFiles  []string `json:",omitempty"` // _test.go source files internal to the package they are testing
+	XTestGoFiles []string `json:",omitempty"` //_test.go source files external to the package they are testing
+	CFiles       []string `json:",omitempty"` // .c source files
+	HFiles       []string `json:",omitempty"` // .h source files
+	SFiles       []string `json:",omitempty"` // .s source files
+	CgoFiles     []string `json:",omitempty"` // .go sources files that import "C"
+	CgoCFLAGS    []string `json:",omitempty"` // cgo: flags for C compiler
+	CgoLDFLAGS   []string `json:",omitempty"` // cgo: flags for linker
+
+	// Dependency information
+	Imports    []string        `json:",omitempty"` // import paths used by this package
+	Deps       []string        `json:",omitempty"` // all (recursively) imported dependencies
+	DepsErrors []*PackageError `json:",omitempty"` // errors loading dependencies
+
+	// Unexported fields are not part of the public API.
+	t       *build.Tree
+	pkgdir  string
+	info    *build.DirInfo
+	imports []*Package
+	deps    []*Package
+	gofiles []string // GoFiles+CgoFiles+TestGoFiles+XTestGoFiles files, absolute paths
+	target  string   // installed file for this package (may be executable)
+	fake    bool     // synthesized package
+}
+
+// A PackageError describes an error loading information about a package.
+type PackageError struct {
+	ImportStack []string // shortest path from package named on command line to this one
+	Err         string   // the error itself
+}
+
+func (p *PackageError) Error() string {
+	return strings.Join(p.ImportStack, "\n\timports ") + ": " + p.Err
+}
+
+// An importStack is a stack of import paths.
+type importStack []string
+
+func (s *importStack) push(p string) {
+	*s = append(*s, p)
+}
+
+func (s *importStack) pop() {
+	*s = (*s)[0 : len(*s)-1]
+}
+
+func (s *importStack) copy() []string {
+	return append([]string{}, *s...)
+}
+
+// shorterThan returns true if sp is shorter than t.
+// We use this to record the shortest import sequence
+// that leads to a particular package.
+func (sp *importStack) shorterThan(t []string) bool {
+	s := *sp
+	if len(s) != len(t) {
+		return len(s) < len(t)
+	}
+	// If they are the same length, settle ties using string ordering.
+	for i := range s {
+		if s[i] != t[i] {
+			return s[i] < t[i]
+		}
+	}
+	return false // they are equal
+}
+
+// packageCache is a lookup cache for loadPackage,
+// so that if we look up a package multiple times
+// we return the same pointer each time.
+var packageCache = map[string]*Package{}
+
+// reloadPackage is like loadPackage but makes sure
+// not to use the package cache.
+func reloadPackage(arg string, stk *importStack) *Package {
+	p := packageCache[arg]
+	if p != nil {
+		delete(packageCache, p.Dir)
+		delete(packageCache, p.ImportPath)
+	}
+	return loadPackage(arg, stk)
+}
+
+// loadPackage scans directory named by arg,
+// which is either an import path or a file system path
+// (if the latter, must be rooted or begin with . or ..),
+// and returns a *Package describing the package
+// found in that directory.
+func loadPackage(arg string, stk *importStack) *Package {
+	stk.push(arg)
+	defer stk.pop()
+
+	// Check package cache.
+	if p := packageCache[arg]; p != nil {
+		return reusePackage(p, stk)
+	}
+
+	// Find basic information about package path.
+	t, importPath, err := build.FindTree(arg)
+	dir := ""
+	// Maybe it is a standard command.
+	if err != nil && strings.HasPrefix(arg, "cmd/") {
+		goroot := build.Path[0]
+		p := filepath.Join(goroot.Path, "src", arg)
+		if st, err1 := os.Stat(p); err1 == nil && st.IsDir() {
+			t = goroot
+			importPath = arg
+			dir = p
+			err = nil
+		}
+	}
+	// Maybe it is a path to a standard command.
+	if err != nil && (filepath.IsAbs(arg) || isLocalPath(arg)) {
+		arg, _ := filepath.Abs(arg)
+		goroot := build.Path[0]
+		cmd := filepath.Join(goroot.Path, "src", "cmd") + string(filepath.Separator)
+		if st, err1 := os.Stat(arg); err1 == nil && st.IsDir() && strings.HasPrefix(arg, cmd) {
+			t = goroot
+			importPath = filepath.FromSlash(arg[len(cmd):])
+			dir = arg
+			err = nil
+		}
+	}
+	if err != nil {
+		p := &Package{
+			ImportPath: arg,
+			Error: &PackageError{
+				ImportStack: stk.copy(),
+				Err:         err.Error(),
+			},
+			Incomplete: true,
+		}
+		packageCache[arg] = p
+		return p
+	}
+
+	if dir == "" {
+		dir = filepath.Join(t.SrcDir(), filepath.FromSlash(importPath))
+	}
+
+	// Maybe we know the package by its directory.
+	if p := packageCache[dir]; p != nil {
+		packageCache[importPath] = p
+		return reusePackage(p, stk)
+	}
+
+	return scanPackage(&buildContext, t, arg, importPath, dir, stk)
+}
+
+func reusePackage(p *Package, stk *importStack) *Package {
+	// We use p.imports==nil to detect a package that
+	// is in the midst of its own loadPackage call
+	// (all the recursion below happens before p.imports gets set).
+	if p.imports == nil {
+		if p.Error == nil {
+			p.Error = &PackageError{
+				ImportStack: stk.copy(),
+				Err:         "import loop",
+			}
+		}
+		p.Incomplete = true
+	}
+	if p.Error != nil && stk.shorterThan(p.Error.ImportStack) {
+		p.Error.ImportStack = stk.copy()
+	}
+	return p
+}
+
+// firstSentence returns the first sentence of the document text.
+// The sentence ends after the first period followed by a space.
+// The returned sentence will have no \n \r or \t characters and
+// will use only single spaces between words.
+func firstSentence(text string) string {
+	var b []byte
+	space := true
+Loop:
+	for i := 0; i < len(text); i++ {
+		switch c := text[i]; c {
+		case ' ', '\t', '\r', '\n':
+			if !space {
+				space = true
+				if len(b) > 0 && b[len(b)-1] == '.' {
+					break Loop
+				}
+				b = append(b, ' ')
+			}
+		default:
+			space = false
+			b = append(b, c)
+		}
+	}
+	return string(b)
+}
+
+func scanPackage(ctxt *build.Context, t *build.Tree, arg, importPath, dir string, stk *importStack) *Package {
+	// Read the files in the directory to learn the structure
+	// of the package.
+	p := &Package{
+		ImportPath: importPath,
+		Dir:        dir,
+		Standard:   t.Goroot && !strings.Contains(importPath, "."),
+		t:          t,
+	}
+	packageCache[dir] = p
+	packageCache[importPath] = p
+
+	info, err := ctxt.ScanDir(dir)
+	if err != nil {
+		p.Error = &PackageError{
+			ImportStack: stk.copy(),
+			Err:         err.Error(),
+		}
+		p.Incomplete = true
+		return p
+	}
+
+	p.info = info
+	p.Name = info.Package
+	p.Doc = firstSentence(info.PackageComment.Text())
+	p.Imports = info.Imports
+	p.GoFiles = info.GoFiles
+	p.TestGoFiles = info.TestGoFiles
+	p.XTestGoFiles = info.XTestGoFiles
+	p.CFiles = info.CFiles
+	p.HFiles = info.HFiles
+	p.SFiles = info.SFiles
+	p.CgoFiles = info.CgoFiles
+	p.CgoCFLAGS = info.CgoCFLAGS
+	p.CgoLDFLAGS = info.CgoLDFLAGS
+
+	if info.Package == "main" {
+		_, elem := filepath.Split(importPath)
+		p.target = filepath.Join(t.BinDir(), elem)
+		if ctxt.GOOS == "windows" {
+			p.target += ".exe"
+		}
+	} else {
+		p.target = filepath.Join(t.PkgDir(), filepath.FromSlash(importPath)+".a")
+	}
+
+	var built time.Time
+	if fi, err := os.Stat(p.target); err == nil {
+		built = fi.ModTime()
+	}
+
+	// Build list of full paths to all Go files in the package,
+	// for use by commands like go fmt.
+	for _, f := range info.GoFiles {
+		p.gofiles = append(p.gofiles, filepath.Join(dir, f))
+	}
+	for _, f := range info.CgoFiles {
+		p.gofiles = append(p.gofiles, filepath.Join(dir, f))
+	}
+	for _, f := range info.TestGoFiles {
+		p.gofiles = append(p.gofiles, filepath.Join(dir, f))
+	}
+	for _, f := range info.XTestGoFiles {
+		p.gofiles = append(p.gofiles, filepath.Join(dir, f))
+	}
+
+	sort.Strings(p.gofiles)
+
+	srcss := [][]string{
+		p.GoFiles,
+		p.CFiles,
+		p.HFiles,
+		p.SFiles,
+		p.CgoFiles,
+	}
+Stale:
+	for _, srcs := range srcss {
+		for _, src := range srcs {
+			if fi, err := os.Stat(filepath.Join(p.Dir, src)); err != nil || fi.ModTime().After(built) {
+				//println("STALE", p.ImportPath, "needs", src, err)
+				p.Stale = true
+				break Stale
+			}
+		}
+	}
+
+	importPaths := p.Imports
+	// Packages that use cgo import runtime/cgo implicitly,
+	// except runtime/cgo itself.
+	if len(info.CgoFiles) > 0 && (!p.Standard || p.ImportPath != "runtime/cgo") {
+		importPaths = append(importPaths, "runtime/cgo")
+	}
+	// Everything depends on runtime, except runtime and unsafe.
+	if !p.Standard || (p.ImportPath != "runtime" && p.ImportPath != "unsafe") {
+		importPaths = append(importPaths, "runtime")
+	}
+
+	// Record package under both import path and full directory name.
+	packageCache[dir] = p
+	packageCache[importPath] = p
+
+	// Build list of imported packages and full dependency list.
+	imports := make([]*Package, 0, len(p.Imports))
+	deps := make(map[string]bool)
+	for _, path := range importPaths {
+		if path == "C" {
+			continue
+		}
+		deps[path] = true
+		p1 := loadPackage(path, stk)
+		imports = append(imports, p1)
+		for _, dep := range p1.Deps {
+			deps[dep] = true
+		}
+		if p1.Stale {
+			p.Stale = true
+		}
+		if p1.Incomplete {
+			p.Incomplete = true
+		}
+		// p1.target can be empty only if p1 is not a real package,
+		// such as package unsafe or the temporary packages
+		// created during go test.
+		if !p.Stale && p1.target != "" {
+			if fi, err := os.Stat(p1.target); err != nil || fi.ModTime().After(built) {
+				//println("STALE", p.ImportPath, "needs", p1.target, err)
+				//println("BUILT", built.String(), "VS", fi.ModTime().String())
+				p.Stale = true
+			}
+		}
+	}
+	p.imports = imports
+
+	p.Deps = make([]string, 0, len(deps))
+	for dep := range deps {
+		p.Deps = append(p.Deps, dep)
+	}
+	sort.Strings(p.Deps)
+	for _, dep := range p.Deps {
+		p1 := packageCache[dep]
+		if p1 == nil {
+			panic("impossible: missing entry in package cache for " + dep + " imported by " + p.ImportPath)
+		}
+		p.deps = append(p.deps, p1)
+		if p1.Error != nil {
+			p.DepsErrors = append(p.DepsErrors, p1.Error)
+		}
+	}
+
+	// unsafe is a fake package and is never out-of-date.
+	if p.Standard && p.ImportPath == "unsafe" {
+		p.Stale = false
+		p.target = ""
+	}
+
+	return p
+}
+
+// packages returns the packages named by the
+// command line arguments 'args'.  If a named package
+// cannot be loaded at all (for example, if the directory does not exist),
+// then packages prints an error and does not include that
+// package in the results.  However, if errors occur trying
+// to load dependencies of a named package, the named
+// package is still returned, with p.Incomplete = true
+// and details in p.DepsErrors.
+func packages(args []string) []*Package {
+	args = importPaths(args)
+	var pkgs []*Package
+	var stk importStack
+	for _, arg := range args {
+		pkg := loadPackage(arg, &stk)
+		if pkg.Error != nil {
+			errorf("%s", pkg.Error)
+			continue
+		}
+		pkgs = append(pkgs, pkg)
+	}
+	return pkgs
+}
+
+// packagesAndErrors is like 'packages' but returns a 
+// *Package for every argument, even the ones that
+// cannot be loaded at all.
+// The packages that fail to load will have p.Error != nil.
+func packagesAndErrors(args []string) []*Package {
+	args = importPaths(args)
+	var pkgs []*Package
+	var stk importStack
+	for _, arg := range args {
+		pkgs = append(pkgs, loadPackage(arg, &stk))
+	}
+	return pkgs
+}
+
+// packagesForBuild is like 'packages' but fails if any of
+// the packages or their dependencies have errors
+// (cannot be built).
+func packagesForBuild(args []string) []*Package {
+	pkgs := packagesAndErrors(args)
+	printed := map[*PackageError]bool{}
+	for _, pkg := range pkgs {
+		if pkg.Error != nil {
+			errorf("%s", pkg.Error)
+		}
+		for _, err := range pkg.DepsErrors {
+			// Since these are errors in dependencies,
+			// the same error might show up multiple times,
+			// once in each package that depends on it.
+			// Only print each once.
+			if !printed[err] {
+				printed[err] = true
+				errorf("%s", err)
+			}
+		}
+	}
+	exitIfErrors()
+	return pkgs
+}
diff --git a/src/cmd/go/run.go b/src/cmd/go/run.go
new file mode 100644
index 000000000..714cd4051
--- /dev/null
+++ b/src/cmd/go/run.go
@@ -0,0 +1,57 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "strings"
+
+var cmdRun = &Command{
+	UsageLine: "run [-a] [-n] [-x] gofiles... [arguments...]",
+	Short:     "compile and run Go program",
+	Long: `
+Run compiles and runs the main package comprising the named Go source files.
+
+The -a flag forces reinstallation of packages that are already up-to-date.
+The -n flag prints the commands but does not run them.
+The -x flag prints the commands.
+
+See also: go build.
+	`,
+}
+
+func init() {
+	cmdRun.Run = runRun // break init loop
+
+	cmdRun.Flag.BoolVar(&buildA, "a", false, "")
+	cmdRun.Flag.BoolVar(&buildN, "n", false, "")
+	cmdRun.Flag.BoolVar(&buildX, "x", false, "")
+}
+
+func runRun(cmd *Command, args []string) {
+	var b builder
+	b.init()
+	i := 0
+	for i < len(args) && strings.HasSuffix(args[i], ".go") {
+		i++
+	}
+	files, cmdArgs := args[:i], args[i:]
+	p := goFilesPackage(files, "")
+	p.target = "" // must build - not up to date
+	a1 := b.action(modeBuild, modeBuild, p)
+	a := &action{f: (*builder).runProgram, args: cmdArgs, deps: []*action{a1}}
+	b.do(a)
+}
+
+// runProgram is the action for running a binary that has already
+// been compiled.  We ignore exit status.
+func (b *builder) runProgram(a *action) error {
+	if buildN || buildX {
+		b.showcmd("", "%s %s", a.deps[0].target, strings.Join(a.args, " "))
+		if buildN {
+			return nil
+		}
+	}
+	run(a.deps[0].target, a.args)
+	return nil
+}
diff --git a/src/cmd/go/script b/src/cmd/go/script
new file mode 100755
index 000000000..340a7e824
--- /dev/null
+++ b/src/cmd/go/script
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+x() {
+	echo '--- ' "$@"
+	"$@"
+	echo '---'
+	echo
+}
+
+x go help
+x go help build
+x go help clean
+x go help install
+x go help fix
+x go help fmt
+x go help get
+x go help list
+x go help test
+x go help version
+x go help vet
+x go help gopath
+x go help importpath
+x go help remote
diff --git a/src/cmd/go/script.txt b/src/cmd/go/script.txt
new file mode 100644
index 000000000..a67214658
--- /dev/null
+++ b/src/cmd/go/script.txt
@@ -0,0 +1,352 @@
+---  go help
+usage: go command [arguments]
+
+go manages Go source code.
+
+The commands are:
+
+    build       compile and install packages and dependencies
+    clean       remove intermediate objects
+    fix         run gofix on packages
+    fmt         run gofmt -w on packages
+    get         download and install packages and dependencies
+    install     install packages and dependencies
+    list        list packages
+    test        test packages
+    version     print Go version
+    vet         run govet on packages
+
+Use "go help [command]" for more information about a command.
+
+Additional help topics:
+
+    gopath      GOPATH environment variable
+    importpath  description of import paths
+    remote      remote import path syntax
+
+Use "go help [topic]" for more information about that topic.
+
+---
+
+---  go help build
+usage: go build [-n] [-v] [importpath...]
+
+Build compiles the packages named by the import paths,
+along with their dependencies, but it does not install the results.
+
+The -n flag prints the commands but does not run them.
+The -v flag prints the commands.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go install, go get, go clean.
+---
+
+---  go help clean
+usage: go clean [-nuke] [importpath...]
+
+Clean removes intermediate object files generated during
+the compilation of the packages named by the import paths,
+but by default it does not remove the installed package binaries.
+
+The -nuke flag causes clean to remove the installed package binaries too.
+
+TODO: Clean does not clean dependencies of the packages.
+
+For more about import paths, see 'go help importpath'.
+---
+
+---  go help install
+usage: go install [-n] [-v] [importpath...]
+
+Install compiles and installs the packages named by the import paths,
+along with their dependencies.
+
+The -n flag prints the commands but does not run them.
+The -v flag prints the commands.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go build, go get, go clean.
+---
+
+---  go help fix
+usage: go fix [importpath...]
+
+Fix runs the gofix command on the packages named by the import paths.
+
+For more about gofix, see 'godoc gofix'.
+For more about import paths, see 'go help importpath'.
+
+To run gofix with specific options, run gofix itself.
+
+See also: go fmt, go vet.
+---
+
+---  go help fmt
+usage: go fmt [importpath...]
+
+Fmt runs the command 'gofmt -w' on the packages named by the import paths.
+
+For more about gofmt, see 'godoc gofmt'.
+For more about import paths, see 'go help importpath'.
+
+To run gofmt with specific options, run gofmt itself.
+
+See also: go fix, go vet.
+---
+
+---  go help get
+usage: go get [importpath...]
+
+Get downloads and installs the packages named by the import paths,
+along with their dependencies.
+
+After downloading the code, 'go get' looks for a tag beginning
+with "go." that corresponds to the local Go version.
+For Go "release.r58" it looks for a tag named "go.r58".
+For "weekly.2011-06-03" it looks for "go.weekly.2011-06-03".
+If the specific "go.X" tag is not found, it uses the latest earlier
+version it can find.  Otherwise, it uses the default version for
+the version control system: HEAD for git, tip for Mercurial,
+and so on.
+
+TODO: Explain versions better.
+
+For more about import paths, see 'go help importpath'.
+
+For more about how 'go get' finds source code to
+download, see 'go help remote'.
+
+See also: go build, go install, go clean.
+---
+
+---  go help list
+usage: go list [-f format] [-json] [importpath...]
+
+List lists the packages named by the import paths.
+
+The default output shows the package name and file system location:
+
+    books /home/you/src/google-api-go-client.googlecode.com/hg/books/v1
+    oauth /home/you/src/goauth2.googlecode.com/hg/oauth
+    sqlite /home/you/src/gosqlite.googlecode.com/hg/sqlite
+
+The -f flag specifies an alternate format for the list,
+using the syntax of package template.  The default output
+is equivalent to -f '{{.Name}} {{.Dir}}'  The struct
+being passed to the template is:
+
+    type Package struct {
+        Name string         // package name
+        Doc string          // package documentation string
+        GoFiles []string    // names of Go source files in package
+        ImportPath string   // import path denoting package
+        Imports []string    // import paths used by this package
+        Deps []string       // all (recursively) imported dependencies
+        Dir string          // directory containing package sources
+        Version string      // version of installed package
+    }
+
+The -json flag causes the package data to be printed in JSON format.
+
+For more about import paths, see 'go help importpath'.
+---
+
+---  go help test
+usage: go test [importpath...]
+
+Test runs gotest to test the packages named by the import paths.
+It prints a summary of the test results in the format:
+
+	test archive/tar
+	FAIL archive/zip
+	test compress/gzip
+	...
+
+followed by gotest output for each failed package.
+
+For more about import paths, see 'go help importpath'.
+
+See also: go build, go compile, go vet.
+---
+
+---  go help version
+usage: go version
+
+Version prints the Go version, as reported by runtime.Version.
+---
+
+---  go help vet
+usage: go vet [importpath...]
+
+Vet runs the govet command on the packages named by the import paths.
+
+For more about govet, see 'godoc govet'.
+For more about import paths, see 'go help importpath'.
+
+To run govet with specific options, run govet itself.
+
+See also: go fmt, go fix.
+---
+
+---  go help gopath
+The GOPATH environment variable lists places to look for Go code.
+On Unix, the value is a colon-separated string.
+On Windows, the value is a semicolon-separated string.
+On Plan 9, the value is a list.
+
+GOPATH must be set to build and install packages outside the
+standard Go tree.
+
+Each directory listed in GOPATH must have a prescribed structure:
+
+The src/ directory holds source code.  The path below 'src'
+determines the import path or executable name.
+
+The pkg/ directory holds installed package objects.
+As in the Go tree, each target operating system and
+architecture pair has its own subdirectory of pkg
+(pkg/GOOS_GOARCH).
+
+If DIR is a directory listed in the GOPATH, a package with
+source in DIR/src/foo/bar can be imported as "foo/bar" and
+has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a".
+
+The bin/ directory holds compiled commands.
+Each command is named for its source directory, but only
+the final element, not the entire path.  That is, the
+command with source in DIR/src/foo/quux is installed into
+DIR/bin/quux, not DIR/bin/foo/quux.  The foo/ is stripped
+so that you can add DIR/bin to your PATH to get at the
+installed commands.
+
+Here's an example directory layout:
+
+    GOPATH=/home/user/gocode
+
+    /home/user/gocode/
+        src/
+            foo/
+                bar/               (go code in package bar)
+                    x.go
+                quux/              (go code in package main)
+                    y.go
+        bin/
+            quux                   (installed command)
+		pkg/
+		    linux_amd64/
+		        foo/
+		            bar.a          (installed package object)
+
+Go searches each directory listed in GOPATH to find source code,
+but new packages are always downloaded into the first directory 
+in the list.
+---
+
+---  go help importpath
+Many commands apply to a set of packages named by import paths:
+
+	go action [importpath...]
+
+An import path that is a rooted path or that begins with
+a . or .. element is interpreted as a file system path and
+denotes the package in that directory.
+
+Otherwise, the import path P denotes the package found in
+the directory DIR/src/P for some DIR listed in the GOPATH
+environment variable (see 'go help gopath'). 
+
+If no import paths are given, the action applies to the
+package in the current directory.
+
+The special import path "all" expands to all package directories
+found in all the GOPATH trees.  For example, 'go list all' 
+lists all the packages on the local system.
+
+An import path can also name a package to be downloaded from
+a remote repository.  Run 'go help remote' for details.
+
+Every package in a program must have a unique import path.
+By convention, this is arranged by starting each path with a
+unique prefix that belongs to you.  For example, paths used
+internally at Google all begin with 'google', and paths
+denoting remote repositories begin with the path to the code,
+such as 'project.googlecode.com/'.
+---
+
+---  go help remote
+An import path (see 'go help importpath') denotes a package
+stored in the local file system.  Certain import paths also
+describe how to obtain the source code for the package using
+a revision control system.
+
+A few common code hosting sites have special syntax:
+
+	BitBucket (Mercurial)
+
+		import "bitbucket.org/user/project"
+		import "bitbucket.org/user/project/sub/directory"
+
+	GitHub (Git)
+
+		import "github.com/user/project"
+		import "github.com/user/project/sub/directory"
+
+	Google Code Project Hosting (Git, Mercurial, Subversion)
+
+		import "project.googlecode.com/git"
+		import "project.googlecode.com/git/sub/directory"
+
+		import "project.googlecode.com/hg"
+		import "project.googlecode.com/hg/sub/directory"
+
+		import "project.googlecode.com/svn/trunk"
+		import "project.googlecode.com/svn/trunk/sub/directory"
+
+	Launchpad (Bazaar)
+
+		import "launchpad.net/project"
+		import "launchpad.net/project/series"
+		import "launchpad.net/project/series/sub/directory"
+
+		import "launchpad.net/~user/project/branch"
+		import "launchpad.net/~user/project/branch/sub/directory"
+
+For code hosted on other servers, an import path of the form
+
+	repository.vcs/path
+
+specifies the given repository, with or without the .vcs suffix,
+using the named version control system, and then the path inside
+that repository.  The supported version control systems are:
+
+	Bazaar      .bzr
+	Git         .git
+	Mercurial   .hg
+	Subversion  .svn
+
+For example,
+
+	import "example.org/user/foo.hg"
+
+denotes the root directory of the Mercurial repository at
+example.org/user/foo or foo.hg, and
+
+	import "example.org/repo.git/foo/bar"
+
+denotes the foo/bar directory of the Git repository at
+example.com/repo or repo.git.
+
+When a version control system supports multiple protocols,
+each is tried in turn when downloading.  For example, a Git
+download tries git://, then https://, then http://.
+
+New downloaded packages are written to the first directory
+listed in the GOPATH environment variable (see 'go help gopath').
+
+The go command attempts to download the version of the
+package appropriate for the Go release being used.
+Run 'go help install' for more.
+---
+
diff --git a/src/cmd/go/test.go b/src/cmd/go/test.go
new file mode 100644
index 000000000..6cd49fe5a
--- /dev/null
+++ b/src/cmd/go/test.go
@@ -0,0 +1,681 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/build"
+	"go/parser"
+	"go/token"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"text/template"
+	"time"
+	"unicode"
+	"unicode/utf8"
+)
+
+// Break init loop.
+func init() {
+	cmdTest.Run = runTest
+}
+
+var cmdTest = &Command{
+	CustomFlags: true,
+	UsageLine:   "test [-c] [-file a.go -file b.go ...] [-p n] [-x] [importpath...] [flags for test binary]",
+	Short:       "test packages",
+	Long: `
+'Go test' automates testing the packages named by the import paths.
+It prints a summary of the test results in the format:
+
+	ok   archive/tar   0.011s
+	FAIL archive/zip   0.022s
+	ok   compress/gzip 0.033s
+	...
+
+followed by detailed output for each failed package.
+
+'Go test' recompiles each package along with any files with names matching
+the file pattern "*_test.go".  These additional files can contain test functions,
+benchmark functions, and example functions.  See 'go help testfunc' for more.
+
+By default, go test needs no arguments.  It compiles and tests the package
+with source in the current directory, including tests, and runs the tests.
+If file names are given (with flag -file=test.go, one per extra test source file),
+only those test files are added to the package.  (The non-test files are always
+compiled.)
+
+The package is built in a temporary directory so it does not interfere with the
+non-test installation.
+
+See 'go help testflag' for details about flags handled by 'go test'
+and the test binary.
+
+See 'go help importpath' for more about import paths.
+
+See also: go build, go vet.
+	`,
+}
+
+var helpTestflag = &Command{
+	UsageLine: "testflag",
+	Short:     "description of testing flags",
+	Long: `
+The 'go test' command takes both flags that apply to 'go test' itself
+and flags that apply to the resulting test binary.
+
+The flags handled by 'go test' are:
+
+	-c  Compile the test binary to test.out but do not run it.
+
+	-file a.go
+	    Use only the tests in the source file a.go.
+	    Multiple -file flags may be provided.
+
+	-p n
+	    Compile and test up to n packages in parallel.
+	    The default value is the number of CPUs available.
+
+	-x  Print each subcommand go test executes.
+
+The resulting test binary, called test.out, has its own flags:
+
+	-test.v
+	    Verbose output: log all tests as they are run.
+
+	-test.run pattern
+	    Run only those tests matching the regular expression.
+
+	-test.bench pattern
+	    Run benchmarks matching the regular expression.
+	    By default, no benchmarks run.
+
+	-test.cpuprofile cpu.out
+	    Write a CPU profile to the specified file before exiting.
+
+	-test.memprofile mem.out
+	    Write a memory profile to the specified file when all tests
+	    are complete.
+
+	-test.memprofilerate n
+	    Enable more precise (and expensive) memory profiles by setting
+	    runtime.MemProfileRate.  See 'godoc runtime MemProfileRate'.
+	    To profile all memory allocations, use -test.memprofilerate=1
+	    and set the environment variable GOGC=off to disable the
+	    garbage collector, provided the test can run in the available
+	    memory without garbage collection.
+
+	-test.parallel n
+	    Allow parallel execution of test functions that call t.Parallel.
+	    The value of this flag is the maximum number of tests to run
+	    simultaneously; by default, it is set to the value of GOMAXPROCS.
+
+	-test.short
+	    Tell long-running tests to shorten their run time.
+	    It is off by default but set during all.bash so that installing
+	    the Go tree can run a sanity check but not spend time running
+	    exhaustive tests.
+
+	-test.timeout t
+		If a test runs longer than t, panic.
+
+	-test.benchtime n
+		Run enough iterations of each benchmark to take n seconds.
+		The default is 1 second.
+
+	-test.cpu 1,2,4
+	    Specify a list of GOMAXPROCS values for which the tests or 
+	    benchmarks should be executed.  The default is the current value
+	    of GOMAXPROCS.
+
+For convenience, each of these -test.X flags of the test binary is
+also available as the flag -X in 'go test' itself.  Flags not listed
+here are passed through unaltered.  For instance, the command
+
+	go test -x -v -cpuprofile=prof.out -dir=testdata -update -file x_test.go
+
+will compile the test binary using x_test.go and then run it as
+
+	test.out -test.v -test.cpuprofile=prof.out -dir=testdata -update
+	`,
+}
+
+var helpTestfunc = &Command{
+	UsageLine: "testfunc",
+	Short:     "description of testing functions",
+	Long: `
+The 'go test' command expects to find test, benchmark, and example functions
+in the "*_test.go" files corresponding to the package under test.
+
+A test function is one named TestXXX (where XXX is any alphanumeric string
+not starting with a lower case letter) and should have the signature,
+
+	func TestXXX(t *testing.T) { ... }
+
+A benchmark function is one named BenchmarkXXX and should have the signature,
+
+	func BenchmarkXXX(b *testing.B) { ... }
+
+An example function is similar to a test function but, instead of using *testing.T
+to report success or failure, prints output to os.Stdout and os.Stderr.
+That output is compared against the function's doc comment.
+An example without a doc comment is compiled but not executed.
+
+Godoc displays the body of ExampleXXX to demonstrate the use
+of the function, constant, or variable XXX.  An example of a method M with
+receiver type T or *T is named ExampleT_M.  There may be multiple examples
+for a given function, constant, or variable, distinguished by a trailing _xxx,
+where xxx is a suffix not beginning with an upper case letter.
+
+Here is an example of an example:
+
+	// The output of this example function.
+	func ExamplePrintln() {
+		Println("The output of this example function.")
+	}
+
+See the documentation of the testing package for more information.
+		`,
+}
+
+var (
+	testC        bool     // -c flag
+	testP        int      // -p flag
+	testX        bool     // -x flag
+	testV        bool     // -v flag
+	testFiles    []string // -file flag(s)  TODO: not respected
+	testArgs     []string
+	testShowPass bool // whether to display passing output
+	testBench    bool
+)
+
+func runTest(cmd *Command, args []string) {
+	var pkgArgs []string
+	pkgArgs, testArgs = testFlags(args)
+
+	// show test PASS output when no packages
+	// are listed (implicitly current directory: "go test")
+	// or when the -v flag has been given.
+	testShowPass = len(pkgArgs) == 0 || testV
+
+	pkgs := packagesForBuild(pkgArgs)
+	if len(pkgs) == 0 {
+		fatalf("no packages to test")
+	}
+
+	if testC && len(pkgs) != 1 {
+		fatalf("cannot use -c flag with multiple packages")
+	}
+
+	buildX = testX
+	if testP > 0 {
+		buildP = testP
+	}
+
+	var b builder
+	b.init()
+
+	var builds, runs, prints []*action
+
+	// Prepare build + run + print actions for all packages being tested.
+	for _, p := range pkgs {
+		buildTest, runTest, printTest, err := b.test(p)
+		if err != nil {
+			errorf("%s", err)
+			continue
+		}
+		builds = append(builds, buildTest)
+		runs = append(runs, runTest)
+		prints = append(prints, printTest)
+	}
+
+	// Ultimately the goal is to print the output.
+	root := &action{deps: prints}
+
+	// Force the printing of results to happen in order,
+	// one at a time.
+	for i, a := range prints {
+		if i > 0 {
+			a.deps = append(a.deps, prints[i-1])
+		}
+	}
+
+	// If we are benchmarking, force everything to
+	// happen in serial.  Could instead allow all the
+	// builds to run before any benchmarks start,
+	// but try this for now.
+	if testBench {
+		for i, a := range builds {
+			if i > 0 {
+				// Make build of test i depend on
+				// completing the run of test i-1.
+				a.deps = append(a.deps, runs[i-1])
+			}
+		}
+	}
+
+	// If we are building any out-of-date packages other
+	// than those under test, warn.
+	okBuild := map[*Package]bool{}
+	for _, p := range pkgs {
+		okBuild[p] = true
+	}
+
+	warned := false
+	for _, a := range actionList(root) {
+		if a.p != nil && a.f != nil && !okBuild[a.p] && !a.p.fake {
+			okBuild[a.p] = true // don't warn again
+			if !warned {
+				fmt.Fprintf(os.Stderr, "warning: building out-of-date packages:\n")
+				warned = true
+			}
+			fmt.Fprintf(os.Stderr, "\t%s\n", a.p.ImportPath)
+		}
+	}
+	if warned {
+		fmt.Fprintf(os.Stderr, "installing these packages with 'go install' will speed future tests.\n\n")
+	}
+
+	b.do(root)
+}
+
+func (b *builder) test(p *Package) (buildAction, runAction, printAction *action, err error) {
+	if len(p.info.TestGoFiles)+len(p.info.XTestGoFiles) == 0 {
+		build := &action{p: p}
+		run := &action{p: p}
+		print := &action{f: (*builder).notest, p: p, deps: []*action{build}}
+		return build, run, print, nil
+	}
+
+	// Build Package structs describing:
+	//	ptest - package + test files
+	//	pxtest - package of external test files
+	//	pmain - test.out binary
+	var ptest, pxtest, pmain *Package
+
+	// go/build does not distinguish the dependencies used
+	// by the TestGoFiles from the dependencies used by the
+	// XTestGoFiles, so we build one list and use it for both
+	// ptest and pxtest.  No harm done.
+	var imports []*Package
+	var stk importStack
+	stk.push(p.ImportPath + "_test")
+	for _, path := range p.info.TestImports {
+		p1 := loadPackage(path, &stk)
+		if p1.Error != nil {
+			return nil, nil, nil, p1.Error
+		}
+		imports = append(imports, p1)
+	}
+	stk.pop()
+
+	// The ptest package needs to be importable under the
+	// same import path that p has, but we cannot put it in
+	// the usual place in the temporary tree, because then
+	// other tests will see it as the real package.
+	// Instead we make a _test directory under the import path
+	// and then repeat the import path there.  We tell the
+	// compiler and linker to look in that _test directory first.
+	//
+	// That is, if the package under test is unicode/utf8,
+	// then the normal place to write the package archive is
+	// $WORK/unicode/utf8.a, but we write the test package archive to
+	// $WORK/unicode/utf8/_test/unicode/utf8.a.
+	// We write the external test package archive to
+	// $WORK/unicode/utf8/_test/unicode/utf8_test.a.
+	testDir := filepath.Join(b.work, filepath.FromSlash(p.ImportPath+"/_test"))
+	ptestObj := filepath.Join(testDir, filepath.FromSlash(p.ImportPath+".a"))
+	pxtestObj := filepath.Join(testDir, filepath.FromSlash(p.ImportPath+"_test.a"))
+
+	// Create the directory for the .a files.
+	ptestDir, _ := filepath.Split(ptestObj)
+	if err := b.mkdir(ptestDir); err != nil {
+		return nil, nil, nil, err
+	}
+	if err := writeTestmain(filepath.Join(testDir, "_testmain.go"), p); err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Test package.
+	if len(p.info.TestGoFiles) > 0 {
+		ptest = new(Package)
+		*ptest = *p
+		ptest.GoFiles = nil
+		ptest.GoFiles = append(ptest.GoFiles, p.GoFiles...)
+		ptest.GoFiles = append(ptest.GoFiles, p.info.TestGoFiles...)
+		ptest.target = ""
+		ptest.Imports = stringList(p.info.Imports, p.info.TestImports)
+		ptest.imports = append(append([]*Package{}, p.imports...), imports...)
+		ptest.pkgdir = testDir
+		ptest.fake = true
+		a := b.action(modeBuild, modeBuild, ptest)
+		a.objdir = testDir + string(filepath.Separator)
+		a.objpkg = ptestObj
+		a.target = ptestObj
+		a.link = false
+	} else {
+		ptest = p
+	}
+
+	// External test package.
+	if len(p.info.XTestGoFiles) > 0 {
+		pxtest = &Package{
+			Name:       p.Name + "_test",
+			ImportPath: p.ImportPath + "_test",
+			Dir:        p.Dir,
+			GoFiles:    p.info.XTestGoFiles,
+			Imports:    p.info.TestImports,
+			t:          p.t,
+			info:       &build.DirInfo{},
+			imports:    imports,
+			pkgdir:     testDir,
+			fake:       true,
+		}
+		pxtest.imports = append(pxtest.imports, ptest)
+		a := b.action(modeBuild, modeBuild, pxtest)
+		a.objdir = testDir + string(filepath.Separator)
+		a.objpkg = pxtestObj
+		a.target = pxtestObj
+	}
+
+	// Action for building test.out.
+	pmain = &Package{
+		Name:    "main",
+		Dir:     testDir,
+		GoFiles: []string{"_testmain.go"},
+		t:       p.t,
+		info:    &build.DirInfo{},
+		imports: []*Package{ptest},
+		fake:    true,
+	}
+	if pxtest != nil {
+		pmain.imports = append(pmain.imports, pxtest)
+	}
+
+	// The generated main also imports testing and regexp.
+	stk.push("testmain")
+	ptesting := loadPackage("testing", &stk)
+	if ptesting.Error != nil {
+		return nil, nil, nil, ptesting.Error
+	}
+	pregexp := loadPackage("regexp", &stk)
+	if pregexp.Error != nil {
+		return nil, nil, nil, pregexp.Error
+	}
+	pmain.imports = append(pmain.imports, ptesting, pregexp)
+
+	a := b.action(modeBuild, modeBuild, pmain)
+	a.objdir = testDir + string(filepath.Separator)
+	a.objpkg = filepath.Join(testDir, "main.a")
+	a.target = filepath.Join(testDir, "test.out") + b.exe
+	pmainAction := a
+
+	if testC {
+		// -c flag: create action to copy binary to ./test.out.
+		runAction = &action{
+			f:      (*builder).install,
+			deps:   []*action{pmainAction},
+			p:      pmain,
+			target: "test.out" + b.exe,
+		}
+		printAction = &action{p: p, deps: []*action{runAction}} // nop
+	} else {
+		// run test
+		runAction = &action{
+			f:          (*builder).runTest,
+			deps:       []*action{pmainAction},
+			p:          p,
+			ignoreFail: true,
+		}
+		printAction = &action{
+			f:    (*builder).printTest,
+			deps: []*action{runAction},
+			p:    p,
+		}
+	}
+
+	return pmainAction, runAction, printAction, nil
+}
+
+// runTest is the action for running a test binary.
+func (b *builder) runTest(a *action) error {
+	args := stringList(a.deps[0].target, testArgs)
+	a.testOutput = new(bytes.Buffer)
+
+	if buildN || buildX {
+		b.showcmd("", "%s", strings.Join(args, " "))
+		if buildN {
+			return nil
+		}
+	}
+
+	if a.failed {
+		// We were unable to build the binary.
+		a.failed = false
+		fmt.Fprintf(a.testOutput, "FAIL\t%s [build failed]\n", a.p.ImportPath)
+		exitStatus = 1
+		return nil
+	}
+
+	cmd := exec.Command(args[0], args[1:]...)
+	cmd.Dir = a.p.Dir
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+
+	t0 := time.Now()
+	err := cmd.Start()
+
+	// This is a last-ditch deadline to detect and
+	// stop wedged test binaries, to keep the builders
+	// running.
+	const deadline = 10 * time.Minute
+
+	tick := time.NewTimer(deadline)
+	if err == nil {
+		done := make(chan error)
+		go func() {
+			done <- cmd.Wait()
+		}()
+		select {
+		case err = <-done:
+			// ok
+		case <-tick.C:
+			cmd.Process.Kill()
+			err = <-done
+			fmt.Fprintf(&buf, "*** Test killed: ran too long.\n")
+		}
+		tick.Stop()
+	}
+	out := buf.Bytes()
+	t1 := time.Now()
+	t := fmt.Sprintf("%.3fs", t1.Sub(t0).Seconds())
+	if err == nil {
+		fmt.Fprintf(a.testOutput, "ok  \t%s\t%s\n", a.p.ImportPath, t)
+		if testShowPass {
+			a.testOutput.Write(out)
+		}
+		return nil
+	}
+
+	fmt.Fprintf(a.testOutput, "FAIL\t%s\t%s\n", a.p.ImportPath, t)
+	exitStatus = 1
+	if len(out) > 0 {
+		a.testOutput.Write(out)
+		// assume printing the test binary's exit status is superfluous
+	} else {
+		fmt.Fprintf(a.testOutput, "%s\n", err)
+	}
+	return nil
+}
+
+// printTest is the action for printing a test result.
+func (b *builder) printTest(a *action) error {
+	run := a.deps[0]
+	os.Stdout.Write(run.testOutput.Bytes())
+	run.testOutput = nil
+	return nil
+}
+
+// notest is the action for testing a package with no test files.
+func (b *builder) notest(a *action) error {
+	fmt.Printf("?   \t%s\t[no test files]\n", a.p.ImportPath)
+	return nil
+}
+
+// isTest tells whether name looks like a test (or benchmark, according to prefix).
+// It is a Test (say) if there is a character after Test that is not a lower-case letter.
+// We don't want TesticularCancer.
+func isTest(name, prefix string) bool {
+	if !strings.HasPrefix(name, prefix) {
+		return false
+	}
+	if len(name) == len(prefix) { // "Test" is ok
+		return true
+	}
+	rune, _ := utf8.DecodeRuneInString(name[len(prefix):])
+	return !unicode.IsLower(rune)
+}
+
+// writeTestmain writes the _testmain.go file for package p to
+// the file named out.
+func writeTestmain(out string, p *Package) error {
+	t := &testFuncs{
+		Package: p,
+		Info:    p.info,
+	}
+	for _, file := range p.info.TestGoFiles {
+		if err := t.load(filepath.Join(p.Dir, file), "_test", &t.NeedTest); err != nil {
+			return err
+		}
+	}
+	for _, file := range p.info.XTestGoFiles {
+		if err := t.load(filepath.Join(p.Dir, file), "_xtest", &t.NeedXtest); err != nil {
+			return err
+		}
+	}
+
+	f, err := os.Create(out)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := testmainTmpl.Execute(f, t); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+type testFuncs struct {
+	Tests      []testFunc
+	Benchmarks []testFunc
+	Examples   []testFunc
+	Package    *Package
+	Info       *build.DirInfo
+	NeedTest   bool
+	NeedXtest  bool
+}
+
+type testFunc struct {
+	Package string // imported package name (_test or _xtest)
+	Name    string // function name
+	Output  string // output, for examples
+}
+
+var testFileSet = token.NewFileSet()
+
+func (t *testFuncs) load(filename, pkg string, seen *bool) error {
+	f, err := parser.ParseFile(testFileSet, filename, nil, parser.ParseComments)
+	if err != nil {
+		return err
+	}
+	for _, d := range f.Decls {
+		n, ok := d.(*ast.FuncDecl)
+		if !ok {
+			continue
+		}
+		if n.Recv != nil {
+			continue
+		}
+		name := n.Name.String()
+		switch {
+		case isTest(name, "Test"):
+			t.Tests = append(t.Tests, testFunc{pkg, name, ""})
+			*seen = true
+		case isTest(name, "Benchmark"):
+			t.Benchmarks = append(t.Benchmarks, testFunc{pkg, name, ""})
+			*seen = true
+		case isTest(name, "Example"):
+			output := n.Doc.Text()
+			if output == "" {
+				// Don't run examples with no output.
+				continue
+			}
+			t.Examples = append(t.Examples, testFunc{pkg, name, output})
+			*seen = true
+		}
+	}
+
+	return nil
+}
+
+var testmainTmpl = template.Must(template.New("main").Parse(`
+package main
+
+import (
+	"regexp"
+	"testing"
+
+{{if .NeedTest}}
+	_test {{.Package.ImportPath | printf "%q"}}
+{{end}}
+{{if .NeedXtest}}
+	_xtest {{.Package.ImportPath | printf "%s_test" | printf "%q"}}
+{{end}}
+)
+
+var tests = []testing.InternalTest{
+{{range .Tests}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}},
+{{end}}
+}
+
+var benchmarks = []testing.InternalBenchmark{
+{{range .Benchmarks}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}},
+{{end}}
+}
+
+var examples = []testing.InternalExample{
+{{range .Examples}}
+	{"{{.Name}}", {{.Package}}.{{.Name}}, {{.Output | printf "%q"}}},
+{{end}}
+}
+
+var matchPat string
+var matchRe *regexp.Regexp
+
+func matchString(pat, str string) (result bool, err error) {
+	if matchRe == nil || matchPat != pat {
+		matchPat = pat
+		matchRe, err = regexp.Compile(matchPat)
+		if err != nil {
+			return
+		}
+	}
+	return matchRe.MatchString(str), nil
+}
+
+func main() {
+	testing.Main(matchString, tests, benchmarks, examples)
+}
+
+`))
diff --git a/src/cmd/go/testflag.go b/src/cmd/go/testflag.go
new file mode 100644
index 000000000..a3cacd657
--- /dev/null
+++ b/src/cmd/go/testflag.go
@@ -0,0 +1,215 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+)
+
+// The flag handling part of go test is large and distracting.
+// We can't use the flag package because some of the flags from
+// our command line are for us, and some are for 6.out, and
+// some are for both.
+
+var usageMessage = `Usage of go test:
+  -c=false: compile but do not run the test binary
+  -file=file_test.go: specify file to use for tests;
+      use multiple times for multiple files
+  -p=n: build and test up to n packages in parallel
+  -x=false: print command lines as they are executed
+
+  // These flags can be passed with or without a "test." prefix: -v or -test.v.
+  -bench="": passes -test.bench to test
+  -benchtime=1: passes -test.benchtime to test
+  -cpu="": passes -test.cpu to test
+  -cpuprofile="": passes -test.cpuprofile to test
+  -memprofile="": passes -test.memprofile to test
+  -memprofilerate=0: passes -test.memprofilerate to test
+  -parallel=0: passes -test.parallel to test
+  -run="": passes -test.run to test
+  -short=false: passes -test.short to test
+  -timeout=0: passes -test.timeout to test
+  -v=false: passes -test.v to test
+`
+
+// usage prints a usage message and exits.
+func testUsage() {
+	fmt.Fprint(os.Stderr, usageMessage)
+	exitStatus = 2
+	exit()
+}
+
+// testFlagSpec defines a flag we know about.
+type testFlagSpec struct {
+	name       string
+	isBool     bool
+	passToTest bool // pass to Test
+	multiOK    bool // OK to have multiple instances
+	present    bool // flag has been seen
+}
+
+// testFlagDefn is the set of flags we process.
+var testFlagDefn = []*testFlagSpec{
+	// local.
+	{name: "c", isBool: true},
+	{name: "file", multiOK: true},
+	{name: "p"},
+	{name: "x", isBool: true},
+
+	// passed to 6.out, adding a "test." prefix to the name if necessary: -v becomes -test.v.
+	{name: "bench", passToTest: true},
+	{name: "benchtime", passToTest: true},
+	{name: "cpu", passToTest: true},
+	{name: "cpuprofile", passToTest: true},
+	{name: "memprofile", passToTest: true},
+	{name: "memprofilerate", passToTest: true},
+	{name: "parallel", passToTest: true},
+	{name: "run", passToTest: true},
+	{name: "short", isBool: true, passToTest: true},
+	{name: "timeout", passToTest: true},
+	{name: "v", isBool: true, passToTest: true},
+}
+
+// testFlags processes the command line, grabbing -x and -c, rewriting known flags
+// to have "test" before them, and reading the command line for the 6.out.
+// Unfortunately for us, we need to do our own flag processing because go test
+// grabs some flags but otherwise its command line is just a holding place for
+// test.out's arguments.
+// We allow known flags both before and after the package name list,
+// to allow both
+//	go test fmt -custom-flag-for-fmt-test
+//	go test -x math
+func testFlags(args []string) (packageNames, passToTest []string) {
+	inPkg := false
+	for i := 0; i < len(args); i++ {
+		if !strings.HasPrefix(args[i], "-") {
+			if !inPkg && packageNames == nil {
+				// First package name we've seen.
+				inPkg = true
+			}
+			if inPkg {
+				packageNames = append(packageNames, args[i])
+				continue
+			}
+		}
+
+		if inPkg {
+			// Found an argument beginning with "-"; end of package list.
+			inPkg = false
+		}
+
+		f, value, extraWord := testFlag(args, i)
+		if f == nil {
+			// This is a flag we do not know; we must assume
+			// that any args we see after this might be flag 
+			// arguments, not package names.
+			inPkg = false
+			if packageNames == nil {
+				// make non-nil: we have seen the empty package list
+				packageNames = []string{}
+			}
+			passToTest = append(passToTest, args[i])
+			continue
+		}
+		switch f.name {
+		case "c":
+			setBoolFlag(&testC, value)
+		case "p":
+			setIntFlag(&testP, value)
+		case "x":
+			setBoolFlag(&testX, value)
+		case "v":
+			setBoolFlag(&testV, value)
+		case "file":
+			testFiles = append(testFiles, value)
+		case "bench":
+			// record that we saw the flag; don't care about the value
+			testBench = true
+		}
+		if extraWord {
+			i++
+		}
+		if f.passToTest {
+			passToTest = append(passToTest, "-test."+f.name+"="+value)
+		}
+	}
+	return
+}
+
+// testFlag sees if argument i is a known flag and returns its definition, value, and whether it consumed an extra word.
+func testFlag(args []string, i int) (f *testFlagSpec, value string, extra bool) {
+	arg := args[i]
+	if strings.HasPrefix(arg, "--") { // reduce two minuses to one
+		arg = arg[1:]
+	}
+	switch arg {
+	case "-?", "-h", "-help":
+		usage()
+	}
+	if arg == "" || arg[0] != '-' {
+		return
+	}
+	name := arg[1:]
+	// If there's already "test.", drop it for now.
+	if strings.HasPrefix(name, "test.") {
+		name = name[5:]
+	}
+	equals := strings.Index(name, "=")
+	if equals >= 0 {
+		value = name[equals+1:]
+		name = name[:equals]
+	}
+	for _, f = range testFlagDefn {
+		if name == f.name {
+			// Booleans are special because they have modes -x, -x=true, -x=false.
+			if f.isBool {
+				if equals < 0 { // otherwise, it's been set and will be verified in setBoolFlag
+					value = "true"
+				} else {
+					// verify it parses
+					setBoolFlag(new(bool), value)
+				}
+			} else { // Non-booleans must have a value.
+				extra = equals < 0
+				if extra {
+					if i+1 >= len(args) {
+						usage()
+					}
+					value = args[i+1]
+				}
+			}
+			if f.present && !f.multiOK {
+				usage()
+			}
+			f.present = true
+			return
+		}
+	}
+	f = nil
+	return
+}
+
+// setBoolFlag sets the addressed boolean to the value.
+func setBoolFlag(flag *bool, value string) {
+	x, err := strconv.ParseBool(value)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go test: illegal bool flag value %s\n", value)
+		usage()
+	}
+	*flag = x
+}
+
+// setIntFlag sets the addressed integer to the value.
+func setIntFlag(flag *int, value string) {
+	x, err := strconv.Atoi(value)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go test: illegal int flag value %s\n", value)
+		usage()
+	}
+	*flag = x
+}
diff --git a/src/cmd/go/vcs.go b/src/cmd/go/vcs.go
new file mode 100644
index 000000000..da35048d5
--- /dev/null
+++ b/src/cmd/go/vcs.go
@@ -0,0 +1,425 @@
+// Copyright 2012 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+// A vcsCmd describes how to use a version control system
+// like Mercurial, Git, or Subversion.
+type vcsCmd struct {
+	name string
+	cmd  string // name of binary to invoke command
+
+	createCmd   string // command to download a fresh copy of a repository
+	downloadCmd string // command to download updates into an existing repository
+
+	tagCmd     []tagCmd // commands to list tags
+	tagDefault string   // default tag to use
+	tagSyncCmd string   // command to sync to specific tag
+}
+
+// A tagCmd describes a command to list available tags
+// that can be passed to tagSyncCmd.
+type tagCmd struct {
+	cmd     string // command to list tags
+	pattern string // regexp to extract tags from list
+}
+
+// vcsList lists the known version control systems
+var vcsList = []*vcsCmd{
+	vcsHg,
+	vcsGit,
+	vcsSvn,
+	vcsBzr,
+}
+
+// vcsByCmd returns the version control system for the given
+// command name (hg, git, svn, bzr).
+func vcsByCmd(cmd string) *vcsCmd {
+	for _, vcs := range vcsList {
+		if vcs.cmd == cmd {
+			return vcs
+		}
+	}
+	return nil
+}
+
+// vcsHg describes how to use Mercurial.
+var vcsHg = &vcsCmd{
+	name: "Mercurial",
+	cmd:  "hg",
+
+	createCmd:   "clone -U {repo} {dir}",
+	downloadCmd: "pull",
+
+	// We allow both tag and branch names as 'tags'
+	// for selecting a version.  This lets people have
+	// a go.release.r60 branch and a go.1 branch
+	// and make changes in both, without constantly
+	// editing .hgtags.
+	tagCmd: []tagCmd{
+		{"tags", `^(\S+)`},
+		{"branches", `^(\S+)`},
+	},
+	tagDefault: "default",
+	tagSyncCmd: "update -r {tag}",
+}
+
+// vcsGit describes how to use Git.
+var vcsGit = &vcsCmd{
+	name: "Git",
+	cmd:  "git",
+
+	createCmd:   "clone {repo} {dir}",
+	downloadCmd: "fetch",
+
+	tagCmd:     []tagCmd{{"tag", `^(\S+)$`}},
+	tagDefault: "master",
+	tagSyncCmd: "checkout {tag}",
+}
+
+// vcsBzr describes how to use Bazaar.
+var vcsBzr = &vcsCmd{
+	name: "Bazaar",
+	cmd:  "bzr",
+
+	createCmd: "branch {repo} {dir}",
+
+	// Without --overwrite bzr will not pull tags that changed.
+	// Replace by --overwrite-tags after http://pad.lv/681792 goes in.
+	downloadCmd: "pull --overwrite",
+
+	tagCmd:     []tagCmd{{"tags", `^(\S+)`}},
+	tagDefault: "revno:-1",
+	tagSyncCmd: "update -r {tag}",
+}
+
+// vcsSvn describes how to use Subversion.
+var vcsSvn = &vcsCmd{
+	name: "Subversion",
+	cmd:  "svn",
+
+	createCmd:   "checkout {repo} {dir}",
+	downloadCmd: "update",
+
+	// There is no tag command in subversion.
+	// The branch information is all in the path names.
+}
+
+func (v *vcsCmd) String() string {
+	return v.name
+}
+
+// run runs the command line cmd in the given directory.
+// keyval is a list of key, value pairs.  run expands
+// instances of {key} in cmd into value, but only after
+// splitting cmd into individual arguments.
+// If an error occurs, run prints the command line and the
+// command's combined stdout+stderr to standard error.
+// Otherwise run discards the command's output.
+func (v *vcsCmd) run(dir string, cmd string, keyval ...string) error {
+	_, err := v.run1(dir, false, cmd, keyval)
+	return err
+}
+
+// runOutput is like run but returns the output of the command.
+func (v *vcsCmd) runOutput(dir string, cmd string, keyval ...string) ([]byte, error) {
+	return v.run1(dir, true, cmd, keyval)
+}
+
+// run1 is the generalized implementation of run and runOutput.
+func (v *vcsCmd) run1(dir string, output bool, cmdline string, keyval []string) ([]byte, error) {
+	m := make(map[string]string)
+	for i := 0; i < len(keyval); i += 2 {
+		m[keyval[i]] = keyval[i+1]
+	}
+	args := strings.Fields(cmdline)
+	for i, arg := range args {
+		args[i] = expand(m, arg)
+	}
+
+	cmd := exec.Command(v.cmd, args...)
+	cmd.Dir = dir
+	if buildX {
+		fmt.Printf("cd %s\n", dir)
+		fmt.Printf("%s %s\n", v.cmd, strings.Join(args, " "))
+	}
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	cmd.Stderr = &buf
+	out := buf.Bytes()
+	err := cmd.Run()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "# cd %s; %s %s\n", dir, v.cmd, strings.Join(args, " "))
+		os.Stderr.Write(out)
+		return nil, err
+	}
+	return out, nil
+}
+
+// create creates a new copy of repo in dir.
+// The parent of dir must exist; dir must not.
+func (v *vcsCmd) create(dir, repo string) error {
+	return v.run(".", v.createCmd, "dir", dir, "repo", repo)
+}
+
+// download downloads any new changes for the repo in dir.
+func (v *vcsCmd) download(dir string) error {
+	return v.run(dir, v.downloadCmd)
+}
+
+// tags returns the list of available tags for the repo in dir.
+func (v *vcsCmd) tags(dir string) ([]string, error) {
+	var tags []string
+	for _, tc := range v.tagCmd {
+		out, err := v.runOutput(dir, tc.cmd)
+		if err != nil {
+			return nil, err
+		}
+		re := regexp.MustCompile(`(?m-s)` + tc.pattern)
+		tags = append(tags, re.FindAllString(string(out), -1)...)
+	}
+	return tags, nil
+}
+
+// tagSync syncs the repo in dir to the named tag,
+// which either is a tag returned by tags or is v.tagDefault.
+func (v *vcsCmd) tagSync(dir, tag string) error {
+	if v.tagSyncCmd == "" {
+		return nil
+	}
+	return v.run(dir, v.tagSyncCmd, "tag", tag)
+}
+
+// A vcsPath describes how to convert an import path into a
+// version control system and repository name.
+type vcsPath struct {
+	prefix string                              // prefix this description applies to
+	re     string                              // pattern for import path
+	repo   string                              // repository to use (expand with match of re)
+	vcs    string                              // version control system to use (expand with match of re)
+	check  func(match map[string]string) error // additional checks
+
+	regexp *regexp.Regexp // cached compiled form of re
+}
+
+// vcsForImportPath analyzes importPath to determine the
+// version control system, and code repository to use.
+// On return, repo is the repository URL and root is the
+// import path corresponding to the root of the repository
+// (thus root is a prefix of importPath).
+func vcsForImportPath(importPath string) (vcs *vcsCmd, repo, root string, err error) {
+	for _, srv := range vcsPaths {
+		if !strings.HasPrefix(importPath, srv.prefix) {
+			continue
+		}
+		m := srv.regexp.FindStringSubmatch(importPath)
+		if m == nil {
+			if srv.prefix != "" {
+				return nil, "", "", fmt.Errorf("invalid %s import path %q", srv.prefix, importPath)
+			}
+			continue
+		}
+
+		// Build map of named subexpression matches for expand.
+		match := map[string]string{
+			"prefix": srv.prefix,
+			"import": importPath,
+		}
+		for i, name := range srv.regexp.SubexpNames() {
+			if name != "" && match[name] == "" {
+				match[name] = m[i]
+			}
+		}
+		if srv.vcs != "" {
+			match["vcs"] = expand(match, srv.vcs)
+		}
+		if srv.repo != "" {
+			match["repo"] = expand(match, srv.repo)
+		}
+		if srv.check != nil {
+			if err := srv.check(match); err != nil {
+				return nil, "", "", err
+			}
+		}
+		vcs := vcsByCmd(match["vcs"])
+		if vcs == nil {
+			return nil, "", "", fmt.Errorf("unknown version control system %q", match["vcs"])
+		}
+		return vcs, match["repo"], match["root"], nil
+	}
+	return nil, "", "", fmt.Errorf("unrecognized import path %q", importPath)
+}
+
+// expand rewrites s to replace {k} with match[k] for each key k in match.
+func expand(match map[string]string, s string) string {
+	for k, v := range match {
+		s = strings.Replace(s, "{"+k+"}", v, -1)
+	}
+	return s
+}
+
+// vcsPaths lists the known vcs paths.
+var vcsPaths = []*vcsPath{
+	// Google Code - new syntax
+	{
+		prefix: "code.google.com/",
+		re:     `^(?P<root>code\.google\.com/p/(?P<project>[a-z0-9\-]+)(\.(?P<subrepo>[a-z0-9\-]+))?)(/[A-Za-z0-9_.\-]+)*$`,
+		repo:   "https://{root}",
+		check:  googleCodeVCS,
+	},
+
+	// Google Code - old syntax
+	{
+		re:    `^(?P<project>[a-z0-9_\-.]+)\.googlecode\.com/(git|hg|svn)(?P<path>/.*)?$`,
+		check: oldGoogleCode,
+	},
+
+	// Github
+	{
+		prefix: "github.com/",
+		re:     `^(?P<root>github\.com/[A-Za-z0-9_.\-]+/[A-Za-z0-9_.\-]+)(/[A-Za-z0-9_.\-]+)*$`,
+		vcs:    "git",
+		repo:   "https://{root}",
+		check:  noVCSSuffix,
+	},
+
+	// Bitbucket
+	{
+		prefix: "bitbucket.org/",
+		re:     `^(?P<root>bitbucket\.org/(?P<bitname>[A-Za-z0-9_.\-]+/[A-Za-z0-9_.\-]+))(/[A-Za-z0-9_.\-]+)*$`,
+		repo:   "https://{root}",
+		check:  bitbucketVCS,
+	},
+
+	// Launchpad
+	{
+		prefix: "launchpad.net/",
+		re:     `^(?P<root>launchpad\.net/((?P<project>[A-Za-z0-9_.\-]+)(?P<series>/[A-Za-z0-9_.\-]+)?|~[A-Za-z0-9_.\-]+/(\+junk|[A-Za-z0-9_.\-]+)/[A-Za-z0-9_.\-]+))(/[A-Za-z0-9_.\-]+)*$`,
+		vcs:    "bzr",
+		repo:   "https://{root}",
+		check:  launchpadVCS,
+	},
+
+	// General syntax for any server.
+	{
+		re: `^(?P<root>(?P<repo>([a-z0-9.\-]+\.)+[a-z0-9.\-]+(:[0-9]+)?/[A-Za-z0-9_.\-/]*?)\.(?P<vcs>bzr|git|hg|svn))(/[A-Za-z0-9_.\-]+)*$`,
+	},
+}
+
+func init() {
+	// fill in cached regexps.
+	// Doing this eagerly discovers invalid regexp syntax
+	// without having to run a command that needs that regexp.
+	for _, srv := range vcsPaths {
+		srv.regexp = regexp.MustCompile(srv.re)
+	}
+}
+
+// noVCSSuffix checks that the repository name does not
+// end in .foo for any version control system foo.
+// The usual culprit is ".git".
+func noVCSSuffix(match map[string]string) error {
+	repo := match["repo"]
+	for _, vcs := range vcsList {
+		if strings.HasSuffix(repo, "."+vcs.cmd) {
+			return fmt.Errorf("invalid version control suffix in %s path", match["prefix"])
+		}
+	}
+	return nil
+}
+
+var googleCheckout = regexp.MustCompile(`id="checkoutcmd">(hg|git|svn)`)
+
+// googleCodeVCS determines the version control system for
+// a code.google.com repository, by scraping the project's
+// /source/checkout page.
+func googleCodeVCS(match map[string]string) error {
+	if err := noVCSSuffix(match); err != nil {
+		return err
+	}
+	data, err := httpGET(expand(match, "https://code.google.com/p/{project}/source/checkout?repo={subrepo}"))
+	if err != nil {
+		return err
+	}
+
+	if m := googleCheckout.FindSubmatch(data); m != nil {
+		if vcs := vcsByCmd(string(m[1])); vcs != nil {
+			// Subversion requires the old URLs.
+			// TODO: Test.
+			if vcs == vcsSvn {
+				if match["subrepo"] != "" {
+					return fmt.Errorf("sub-repositories not supported in Google Code Subversion projects")
+				}
+				match["repo"] = expand(match, "https://{project}.googlecode.com/svn")
+			}
+			match["vcs"] = vcs.cmd
+			return nil
+		}
+	}
+
+	return fmt.Errorf("unable to detect version control system for code.google.com/ path")
+}
+
+// oldGoogleCode is invoked for old-style foo.googlecode.com paths.
+// It prints an error giving the equivalent new path.
+func oldGoogleCode(match map[string]string) error {
+	return fmt.Errorf("invalid Google Code import path: use %s instead",
+		expand(match, "code.google.com/p/{project}{path}"))
+}
+
+// bitbucketVCS determines the version control system for a
+// BitBucket repository, by using the BitBucket API.
+func bitbucketVCS(match map[string]string) error {
+	if err := noVCSSuffix(match); err != nil {
+		return err
+	}
+
+	var resp struct {
+		SCM string `json:"scm"`
+	}
+	url := expand(match, "https://api.bitbucket.org/1.0/repositories/{bitname}")
+	data, err := httpGET(url)
+	if err != nil {
+		return err
+	}
+	if err := json.Unmarshal(data, &resp); err != nil {
+		return fmt.Errorf("decoding %s: %v", url, err)
+	}
+
+	if vcsByCmd(resp.SCM) != nil {
+		match["vcs"] = resp.SCM
+		if resp.SCM == "git" {
+			match["repo"] += ".git"
+		}
+		return nil
+	}
+
+	return fmt.Errorf("unable to detect version control system for bitbucket.org/ path")
+}
+
+// launchpadVCS solves the ambiguity for "lp.net/project/foo". In this case,
+// "foo" could be a series name registered in Launchpad with its own branch,
+// and it could also be the name of a directory within the main project
+// branch one level up.
+func launchpadVCS(match map[string]string) error {
+	if match["project"] == "" || match["series"] == "" {
+		return nil
+	}
+	_, err := httpGET(expand(match, "https://code.launchpad.net/{project}{series}/.bzr/branch-format"))
+	if err != nil {
+		match["root"] = expand(match, "launchpad.net/{project}")
+		match["repo"] = expand(match, "https://{root}")
+	}
+	return nil
+}
diff --git a/src/cmd/go/version.go b/src/cmd/go/version.go
new file mode 100644
index 000000000..09e2f1633
--- /dev/null
+++ b/src/cmd/go/version.go
@@ -0,0 +1,25 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"runtime"
+)
+
+var cmdVersion = &Command{
+	Run:       runVersion,
+	UsageLine: "version",
+	Short:     "print Go version",
+	Long:      `Version prints the Go version, as reported by runtime.Version.`,
+}
+
+func runVersion(cmd *Command, args []string) {
+	if len(args) != 0 {
+		cmd.Usage()
+	}
+
+	fmt.Printf("go version %s\n", runtime.Version())
+}
diff --git a/src/cmd/go/vet.go b/src/cmd/go/vet.go
new file mode 100644
index 000000000..52c320032
--- /dev/null
+++ b/src/cmd/go/vet.go
@@ -0,0 +1,30 @@
+// Copyright 2011 The Go Authors.  All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+var cmdVet = &Command{
+	Run:       runVet,
+	UsageLine: "vet [importpath...]",
+	Short:     "run govet on packages",
+	Long: `
+Vet runs the govet command on the packages named by the import paths.
+
+For more about govet, see 'godoc govet'.
+For more about import paths, see 'go help importpath'.
+
+To run govet with specific options, run govet itself.
+
+See also: go fmt, go fix.
+	`,
+}
+
+func runVet(cmd *Command, args []string) {
+	for _, pkg := range packages(args) {
+		// Use pkg.gofiles instead of pkg.Dir so that
+		// the command only applies to this package,
+		// not to packages in subdirectories.
+		run("govet", relPaths(pkg.gofiles))
+	}
+}